MPs have voted in favour of laws to ban prison officers from striking.

As the debate on the Criminal Justice and Immigration Bill gets underway in the Commons, 481 members backed an amendment to outlaw officers from striking.

Some 46 MPs voted against the measure, giving the government a majority of 435.

Justice secretary Jack Straw introduced the amendment following a surprise walkout by 20,000 staff in August.

The move, which would reinstate a Conservative-imposed ban overturned in 2005, has been described by the Tories as a "humiliating U-turn".

Straw denied that suggestion, telling MPs that when the original ban was repealed the Prison Officers Association (POA) was told it would be reintroduced if the voluntary agreement broke down.

The justice secretary told MPs that ministers had been involved in "a series of very intensive negotiations" with the POA to reach a voluntary agreement rather than refusing them the right to strike.

"Throughout the negotiations with the Prison Officers Association, at every stage, it was made clear that the voluntary agreement to which we could assent had to include a very comprehensive and legally binding undertaking by the Prison Officers Association not to take industrial action and it was only in respect of that that the government moved to repeal Section 127 of the 1994 Act," he added.

Calling on Labour MPs to support "what is a reserve power in the event that we are not able to reach a new voluntary agreement", he said public safety was jeopardised when officers went on strike.

Straw warned that the summer strike had also posed a "very considerable risk to prisoners".

"They get locked in their cells with no idea when the next meal is coming or when the next exercise is coming and, for the quite large number of prisoners who have health needs, when their next medication is coming," he added.

MPs also voted through moves to clarify the law on defending properties from intruders to back so-called 'have-a-go-heroes'.

Blasphemy laws

Other controversial amendments relate to plans to change the "outdated" blasphemy laws.

Downing Street said the government has no intention of changing the laws but said ministers would be consulting with the Church of England and others.

Liberal Democrat Evan Harris is leading calls to abolish the legislation, said: "There is cross-party, secular and religious support for confining this unnecessary, discriminatory and censorious law to the history books where it belongs.

"Neither the Church of England nor the government has given a good reason for the blasphemy law to be retained, so it is time Parliament stood up for free expression and against a religious privilege which protects beliefs instead of people."

The legislation could also see the ban on hatred extended to cover transgendered people, as well as creating no-go areas for prostitution.

And the Tories want the Bill to include measures to ensure prisoners serve their full sentences.