Media playback is unsupported on your device Media caption Immigration Minister Damian Green: ''It is a small group in the union leadership that is behaving disgracefully''

Thousands of Home Office staff will strike over job cuts and other issues the day before the Olympics, the Public and Commercial Services union has said.

PCS members will strike for 24 hours next Thursday - when many thousands of visitors are due to arrive in the UK.

Home Secretary Theresa May said the action was "shameful" as it threatens disruption to people travelling to London for the Games.

Immigration minister Damian Green said contingency plans were in place.

The PCS is in dispute with the Home Office over plans to cut 8,500 jobs and the threat of compulsory redundancies in the passport office in Newport, South Wales.

There are also disagreements over pay rises capped at 1% following a two-year wage freeze, privatisation of services, and alleged victimisation of union reps.

East Midlands Trains staff have also voted to strike during the Olympics.

PCS union members will take other forms of action from July 27 to August 20, including working-to-rule and an overtime ban.

The PCS said 57.2% of those who voted backed strike action - the turnout was 20%.

The action will involve staff across the Home Office, including the UK Border Agency, the Identity and Passport Service and Criminal Records Bureau.

'Breaking point'

PCS general secretary Mark Serwotka told the BBC: "I think the government is whipping up hysteria about the Olympics, there'll be no disruption to the Olympics, this is a 24-hour strike before the Olympics actually takes place."

He said he was prepared to meet the culture secretary and home secretary any time in the next week to avert a strike but if they kept their "heads in the sand" the strike would continue.

People should not be disrupting the Olympic Games Ed Miliband, Labour leader

Mr Hunt said the union's behaviour was "totally irresponsible... To threaten us in this way is totally inappropriate.

"To suggest that it won't cause disruption is so extraordinary that it completely beggars belief."

London Mayor Boris Johnson has said he does not think the union will succeed in disrupting the Olympics and the majority of PCS members want to put on a great Games.

In other developments as the UK prepares for the start of the Olympics on Friday 27 July:

Mr Green said there was low turnout in the strike ballot which showed most union members did not support a strike.

He told BBC Two's Newsnight: "PCS members don't want this strike to happen - seven out of eight of them didn't vote for a strike.

"They are patriotic people, they care about their job, they care about the reputation of this country.

"It's a small group in the union leadership that is behaving disgracefully, trying to make political capital out of the Olympics which is meant to be a great national celebration."

Media playback is unsupported on your device Media caption Mark Serwotka: "One day's disruption is better than a year of inadequate services"

Mr Green said he was confident disruption at immigration desks could be minimised because extra staff from the Home Office and other departments had been trained to provide cover.

Mrs May condemned the action saying: "I think that is shameful, frankly. They are holding a strike on what is one of the key days for people coming in for the Olympic Games.

"We will of course put contingency arrangements in place to ensure we can deal with people coming through the border as smoothly as possible."

John Cridland, director general of the Confederation of British Industries, said: "For PCS to go on strike on this key day beggars belief. For it to happen because of a vote by 11% of staff is simply outrageous."

But Labour MP John McDonnell, who chairs the PCS Parliamentary Group, said: "the government has brought this dispute on its own head".

Image caption More troops have been put on standby for possible security duties

East Midlands Trains drivers from the union Aslef plan to strike on 6-8 August in a row over pensions. But South West Trains staff have voted not to strike over the Olympics.

Prime Minister David Cameron insisted the Olympics would be safe and secure.

Speaking at a press conference in Afghanistan, he said: "I do not believe it will be right, I do not believe it will be justified."

Labour leader Ed Miliband also condemned the strike.

This week the National Audit Office said the UK Border Agency had laid off 1,000 more staff than intended and was having to hire extra people and increase overtime to meet its workload.

The PCS is one of the largest unions in the UK with around 250,000 public sector members.

PCS members at the Department for Transport have been taking industrial action over the past few weeks, while staff in other departments, including the ministries of defence and justice, are set to vote shortly on how to campaign against cuts.