A national safety operation is under way to identify buildings with cladding akin to that used on the Grenfell Tower.

So far the Government has received samples from 11 high rise buildings in eight local authority areas where the cladding has failed

safety tests.

Cladding at two high-rise buildings in Portsmouth - Horatia House and Leamington House - is being removed as a precaution after tests revealed a fire risk, Portsmouth City Council said.

Letters were being sent to residents living in the two blocks explaining the measures being taken. The city council's deputy leader Luke Stubbs said no other blocks were affected.

Mr Stubbs said: "Like all councils, we have been working with the Government and fire service to review our buildings.

"As a precaution we submitted some cladding for testing and the results that came back said the cladding on Horatia House and Leamington House was a fire risk.

"As a result we are removing the cladding from those buildings. Protection of Portsmouth's residents is our number one priority and we will not comprise on safety standards.

"We will be removing the cladding as quickly as we can. In the meantime, we would like to reassure residents we have conducted a full assessment of the buildings, with Hampshire Fire and Rescue Service, and the buildings are safe to stay in with all of the existing safety measures still in place."

In every fire that has broken out in city council tower blocks in the past few years, the blaze has been contained within the property where the fire broke out, he added.

Mr Stubbs went on: "As an extra precaution council staff will be present in the two buildings 24 hours a day, for as long as necessary."

Here are some of the buildings where problem cladding has been identified:

:: London

Chalcots estate, Swiss Cottage - Camden Council said it will immediately begin preparing to remove cladding from five towers on the estate, with 24/7 fire patrols carried out until all the panels have been removed.

Rivers Apartments, in Tottenham - Newlon Housing Trust confirmed the 22-storey tower block was clad with the same cladding reportedly used on Grenfell Tower. But it said, after an "extensive safety audit", London Fire Brigade confirmed the tower block would be considered a "low fire risk" after modifications and technical clarifications.

:: Manchester

Village 135 development, Wythenshawe - Wythenshawe Community Housing Group said 78 panels were being removed from a small area of the overall development.

:: Plymouth

Mount Wise Tower Estate - Plymouth Community Homes said it will be removing the combustible elements of cladding from the three 16-storey blocks as soon as possible.

:: Salford

Cladding on nine high-rise blocks in the Pendleton area of Salford has been identified as being made from Aluminium Composite Material (ACM), the material used on Grenfell Tower.

Samples of the cladding are being sent to the Department for Communities and Local Government to be tested independently by fire experts.

Pendleton Together, the management company that runs the blocks in Salford, said they realised questions about the cladding were a "real concern" for residents.

Yesterday, the firm said every householder in a high-rise block is to have a home visit to carry out basic fire safety checks on doors and smoke alarms, while patrols of buildings are being carried out "as a precautionary safety measure".

The same firm runs a number of high-rise blocks in Yorkshire and Lancashire, along with Salford.

:: Sheffield

Harold Lambert Court in the Park Hill area of the city is being checked by the management firm, Together Housing, with cladding samples sent off for analysis.

:: Halifax

Three blocks in Lower Mixenden, a village outside Halifax, are being checked by independent contractors. Together Housing which manages the properties, Jumples Court, Mixenden Court and Wheatley Court, say they are submitting samples of the cladding but an initial visual inspection suggests it is not the same type as that used on the Grenfell Tower.

:: Islington

Islington Council said cladding was to be removed from Braithwaite House, one of eight blocks tested, after it was found to have aluminium composite material.

Test results from the other blocks, Harvist Estate and Brunswick Estate, are yet to be returned, a spokesman said.

Councillor Diarmaid Ward said: "Last night we received results of tests on cladding on the side of Braithwaite House, and they have confirmed the presence of Aluminium Composite Material (ACM).

"We're arranging to have the cladding, which is only on the sides of the building, removed as soon as we possibly can by a specialist contractor.

"We're also stepping up safety measures in the block immediately, with fire safety patrols taking place day and night from today until the panels are removed.

"Our housing staff were at Braithwaite House last night to carry out fire checks and clear any obstructions in communal areas. We're also taking advice from London Fire Brigade and will follow all their recommendations."

:: Newham

Ferrier Point tower in east London was found to have cladding panels with aluminium composite made by Alucobond, it is understood.

Refurbishment on the building, including cladding, was overseen by Rydon, the company involved in the refit of Grenfell Tower.

The insulation behind the cladding, however, was said to be highly fire resistant Rockwool Duoslab.

Rydon did not respond to calls and emails from the Press Association requesting comment.

Two other buildings out of the 88 in the borough are said to have ACM cladding, a spokeswoman said.

She added: "We are following the process as set out by DCLG for sample testing of buildings with ACM cladding.

"Once the results are known, we will take whatever action is necessary to ensure our residents are safe.

"We have already written to tenants and leaseholders in the three blocks explaining what is going on and will keep them informed of all developments."

:: Barnet

Three towers in Barnet, north-east London, were found to have similar rain screen panels on their cladding as Grenfell Tower, but a non-combustible insulation material.

The Granville Point, Harpenmead Point and Templemead Point blocks had all been reclad in 2012, Barnet Council said.

"In line with the Government's advice to councils, samples from the investigation will be submitted to DCLG," a spokesman said.

:: Hounslow

Cladding at a tower in Clements Court, Hounslow, failed the fire-safety test and will be removed "as soon as possible", the borough's council said.

Leader of Hounslow Council Steve Curran said in a statement: "We were informed late last night by the DCLG that the sample of the outer 'Aluminium Composite Material' (ACM) cladding used on Clements Court tower has failed the Building Research Establishment combustion test.

"The outer shell cladding is made up of two thin aluminium sheets with polyethylene filler in between them.

"However, the insulation material behind this outer cladding is a 'rockwool' material which is a non-combustible product, unlike the case of the Grenfell Tower, where the insulation was a combustible type.

"We have, therefore, decided that we will take steps to remove the outer cladding from the building as soon as is practical.

"We are currently looking into how best and swiftly this can be done."

A fire watch patrol will be set up by the authority and safety tests will be carried out on homes, he added.