The Tories have claimed Jeremy Corbyn would "dismantle" Britain's defences and fail to deal with terrorism after the Labour leader refused to say whether he would authorise a drone strike on the leader of Islamic State.
Cabinet minister Damian Green told Sophy Ridge on Sunday: "You just have to listen to what Jeremy Corbyn said this morning - he said that he would dismantle Britain's nuclear defences and he would fail to deal effectively with terrorism.
"This man could be Prime Minister in seven weeks and I can't think of a better reason for sticking with the strong leadership of Theresa May than the fact that Jeremy Corbyn would dismantle this country's defences."
The Labour leader repeatedly refused to be drawn on whether he would be prepared to authorise a drone strike on the leader of IS, Abu Bakr al Baghdadi, if British intelligence discovered his whereabouts.
Speaking on the BBC's Andrew Marr Show, he said: "What is the objective here? Is the objective to start more strikes which may kill many innocent people, as has happened, or is the objective to get a political solution in Syria? Approach it from that position."
Mr Corbyn also suggested he could suspend RAF airstrikes on Islamic State in Syria and Iraq.
He said his priority would be to urge US President Donald Trump to resume international peace talks on Syria in Geneva.
"I would say to President Trump: 'Listen, it's in nobody's interests for this war to continue. Let's get the Geneva process going quickly. In the meantime, no more strikes. Have the UN investigation into the war crime of the use of chemical weapons in Syria and take it on from there.'"
The Labour leader raised the prospect that, if elected Prime Minister on 8 June, he would scrap Britain's Trident nuclear deterrent during the interview.
But shortly afterwards, a Labour spokesman said the party still supported the renewal of the deterrent.
Mr Corbyn earlier revealed he would seek to create four new UK-wide bank holidays on the patron saint's day of each of the home nations.
Meanwhile, the Conservatives have confirmed that a policy to cap energy bills will be in their manifesto.
Mr Green said: "I think people feel some of the big energy companies have taken advantage of them with the tariffs they've got."
Reports suggest that Theresa May will try to reduce bills by about £100 a year for up to 17 million families by capping gas and electricity for households on standard variable tariffs.
The Work and Pensions Secretary went on to say it was different to Ed Miliband's policy of freezing bills which was unveiled at the 2015 General Election.
He explained: "The difference is that we would have Ofgem setting a limit so it would be a cap, more flexible, and able to reflect market conditions so the market would still have an influence.
"That would mean, in practical terms, if the oil price fell again then consumers would benefit in a way they wouldn't have done under Ed Miliband's proposal."