Boris Johnson has said the Tories will be able to provide the security Brits need in "uncertain and unstable times".
Without directly attacking Jeremy Corbyn, the Foreign Secretary hinted at the dividing policies between the Labour leader and Mrs May when he hailed her commitment to the Trident nuclear deterrent and the Nato military alliance.
He also insisted that the Tory leader was best placed to handle the Brexit negotiations - although he acknowledged they would be difficult and "some plaster may fall off the ceiling".
At the Lord Mayor's banquet at Mansion House in the City of London, Mr Johnson told assembled diplomats that a "serious and clear-sighted" approach was needed to deal with issues including the conflict in Syria, the battle against Islamic State and Russia's actions in Ukraine.
In reference to the June 8 general election he said "clear leadership" was needed to "navigate this age of uncertainty".
He said: "We are determined to provide that leadership, to give people the security and certainty they need.
“There can be no more important task for a government than to keep people safe - and we must be prepared to do everything necessary to do so.
"It is why the Prime Minister made it a priority when she took office last year to ensure the renewal of Britain's crucial independent nuclear deterrent and to lead the debate in Parliament.
"It is why she made it clear in the US earlier this year that Britain saw our profound security and defence alliance with the US as part of the bedrock of global security in the modern world."
Mr Johnson said the Conservatives had a "clear plan for Brexit" and the Prime Minister had set out her desire "to get a good deal that works for both Britain and our European friends".