Theresa May warned last night that lives will be in danger if Britain is saddled with a hung Parliament unable to pass anti-terror laws.

The Home Secretary said new legislation was urgently needed to update the powers of MI5 and GCHQ, and repair the damage done by the US traitor Edward Snowden.

But, based on current polling, Parliament would be left deadlocked – with the balance of power held by Scottish nationalists opposed to updating the law.

Home secretary Theresa May (pictured) warned that lives will be in danger if Britain is saddled with a hung Parliament unable to pass anti-terror laws - adding new legislation for MI5 and GCHQ is urgently needed

She urged wavering Ukip supporters and the four in ten voters who say they are still undecided to realise what is at stake for Britain’s security on May 7.

The situation is made especially acute by a ‘poison pill’ inserted into emergency anti-terror laws passed last year. The legislation lapses next year.

And if MPs cannot agree on a replacement, Britain’s spies will be unable to properly track the communications of Islamic State and other terrorists.

Mrs May said that, in the worst scenario, the decision would be in the hands of a minority Ed Miliband government propped up by the SNP – which is opposed to new data retention powers,

Her comments follow a controversial warning by Defence Secretary Michael Fallon that Labour might be unable to renew the Trident nuclear deterrent if it is reliant on Nicola Sturgeon’s SNP – as the polls say is highly likely.

Defence Secretary Michael Fallon (pictured) said Labour might be unable to renew the Trident nuclear deterrent if it is reliant on Sturgeon’s SNP

Mr Fallon said that, having stabbed his brother in the back to get the Labour leadership, Mr Miliband may now do the same to his country over national security.

However Mrs May insists that she is not using counter-terrorism as a ‘political football’ and the threat is real.

She told the Mail: ‘It is a matter of very real concern to me. There is a concern where we have a hung Parliament where it is difficult to get legislation through or a Labour government that is propped up by the SNP.

‘Decisions will need to be taken about the capabilities we need and the one party that is committed to ensuring the security agencies and law enforcement have the powers that we need is the Conservative party.’

Mrs May delivered her warning in an exclusive interview with the Mail during a tour of marginal seats in the North and the Midlands.

In a question and answer session with sixth formers in Bury, she was asked by a student what her opinion was of Snowden – who leaked millions of documents exposing sensitive spying techniques. In her most forthright comments yet, Mrs May replied: ‘As a result of what he has done, it has become more difficult for our security agencies to do the job they need to do to keep us safe. He has potentially put lives at risk.’

The anti-terror law due to expire next year is the Data Retention and Investigatory Powers Act, passed as emergency legislation in 2014.

It gives security officials access to a treasure trove of communications data collected and stored by mobile phone and internet companies. This includes information on who you call, when, for how long and roughly where you were at the time.

It is used for checking alibis, tracing kidnap victims and – in the case of terrorists – identifying and tracking plots. Security agencies say that without it, fanatics will be far harder to monitor and lives will be in danger.

In the wake of the Snowden controversy, some technology firms have been reluctant to help the security services.

Officials say the leaks by Snowden, made to the Guardian, have been a gift for terrorists.