BIN collections and street cleaning in Southampton could grind to a halt because of a wave of crippling strikes over mass pay cuts for council staff.

Galleries and libraries could also shut after union leaders last night threatened targeted walkouts in May that could last for weeks.

Thousands of union members will be balloted on “most serious industrial action” ever seen in the city after Southampton City Council yesterday told staff it will on Monday give them 90 days to sign new contracts cutting their pay and conditions. The new, worse terms would start on July 1.

Members of Unison and Unite unions last month voted 1,552 to 307 to overwhelmingly reject proposed pay cuts of between two and 5.5 per cent. GMB members also rejected them.

Under the cuts the higher paid will be hit hardest, although those earning under £17,500 will get a £250 pay rise. Allowances will also be reduced.

Unison branch secretary Mike Tucker said: “The cuts are substantial and council workers cannot afford to have their pay reduced by that amount”.

He warned of mass day-long walkouts and industrial action by workers providing “key services”

lasting for weeks.

Unite convenor Mark Wood, who represents binmen, street cleaners and park rangers, added: “We intend to use our members to the utmost degree.

“There is no point in taking action unless we will have a telling effect on services. We are looking at a prolonged period of targeted action in specific services.”

Unions are also preparing legal challenges and a street protest on March 24. They are urging all staff to hold off signing new contracts.

Ruling Tories agreed to dismiss staff and re-hire them on worse contracts to force through the cuts to pay and allowances, worth up to £6.6m a year.

The have pledged no “further changes to terms and conditions during this administration” related to budget savings.

The move will help plug a £25m budget hole in 2011/12 following harsh Government funding cuts.

The council’s budget will see 250 jobs go out of the council’s 6,627 workforce, excluding teachers.

That includes up to 40 senior managers and will save £5m.

Council leader Royston Smith said the pay cuts will save a further 400 jobs losses over the next two years. He said despite the cuts, the council was spending more money than ever in roads and pavements, protecting its libraries and leisure centres from closure, keeping its Sure Start centres, maintaining its weekly bin collections and hiring social workers.

He said: “I understand that some staff are concerned about taking a modest pay cut. However the alternative of losing hundreds of jobs and services is something I can’t consider.”