Boris Johnson has made an impassioned plea to keep the UK together, warning Scottish independence would be "an utter catastrophe for this country".
"We will all have lost a way of thinking about ourselves, a way of explaining ourselves to the world," the Mayor of London wrote in the Daily Telegraph.
"We are on the verge of trashing our global name and brand in an act of self-mutilation that will leave our international rivals stunned, gleeful and discreetly scornful."
A co-ordinator for the Back Heathrow campaign, which is calling for expansion of the airport, has called Boris Johnson's candidacy a "slap in the face".
Boris Johnson's selfish plan to stand in the same borough as Heathrow is a slap in the face to tens of thousands of people in west London.
These people rely on Britain's hub airport and the Mayor wants to close it which would result in more than 100,000 people losing their jobs including many in Uxbridge and South Ruislip.
Heathrow's bogeyman may win the selection battle but he won't get his way.
Labour has said that Boris Johnson's bid to become a Tory MP is "confirmation of how weak David Cameron is and how out of touch the Tories are".
The party's London spokesman Sadiq Khan accused Conservative politicians of "jockeying for position in a future leadership contest" instead of tackling the "cost of living crisis".
Boris Johnson is seeking to become Conservative candidate for Uxbridge and South Ruislip at next-year's general election, his spokesman has confirmed.
The Mayor of London confirmed he wanted to stand for Parliament earlier this month, with David Cameron saying it was "great news" that one of his "star players" was returning to the Commons.
Mr Johnson said he hoped to "make his case" that he was the best person to represent the constituency, held by Sir John Randall with a majority of 11,000 at the last general election.
"I'm sure there will be plenty of excellent candidates and I hope very much to make my case to the association," he told the Evening Standard.
Boris Johnson has said tougher laws are needed to combat the threat of British extremists who leave to fight for the Islamic State.
Writing in the Daily Telegraph, Mr Johnson said control orders should be brought back immediately for the most serious cases.
The Mayor of London said those who travel to fight for the terrorist group should be stripped of their citizenship - echoing calls from senior Tory MP David Davis.
Johnson said there should be a "swift and minor change to the law" so that there is a "rebuttable presumption" that those who have travelled to Iraq and Syria, without notifying the authorities, have done so for a "terrorist purpose".
Johnson warned that unless Britain acts to "close down" the Islamic State, the "tide of terror will eventually lap at our own front door."
More than half of voters in a London constituency which is seen as a target for Boris Johnson would vote for him if he chose to stand there in 2015, according to a poll.
A survey conducted in Uxbridge and South Ruislip after the London Mayor finally confirmed his desire to return to the Commons showed he could significantly boost Tory support.
But a third of those who backed him also said he should quit City Hall if elected - despite Mr Johnson insisting he could see out the final year of his term.
The poll of 1,000 people in the seat being vacated by former deputy chief whip John Randall was carried out for Tory donor and former party vice chairman Lord Ashcroft.
The Ipsos-MORI survey for the Evening Standard shows a leap in support for the Tories if London's mayor replaced David Cameron as leader.Read the full story ›
Two in five British people wish more politicians were like Boris Johnson, a ComRes poll for ITV News has found.
Some 28% of Britons believe Mr Johnson - who recently announced his intention to return to parliament - would make a better Prime Minister than David Cameron while 44% think he would be better-suited to the role than Ed Miliband.
More Britons think the Mayor of London is weirder than any of the four main party leaders, with a third saying Mr Johnson is not a serious politician.
But 35% said they would like to see Boris Johnson representing the UK on the global stage.
He was also found to be the second most trusted politician on the economy behind David Cameron, according to the poll of 2,031 British adults.
Nick Clegg has called Boris Johnson a "conventional" politician who "treats his political ambition a bit like he treats his hair."
Clegg said the Mayor of London, who announced his intention to stand at the next General Election, liked to pretend he did not care about his appearance or career - but was actually "fixated" with them.
"The thing about Boris Johnson is despite all the kind of clumsiness and bumbliness, he's actually a really, really ambitious politician," the Deputy Prime Minister said on his regular LBC radio phone in.
"He wants everyone to think that he doesn't really care, but he actually really, really does care."
Boris Johnson could become Business Secretary if the Conservatives win next year's general election, reports suggest.
Following the Johnson's announcement that he will seek to return to parliament next year, the Daily Telegraph report that he could fill the role of Business Secretary when his term as London Mayor ends in 2016.
Mr Johnson would be given an "over-arching role" in charge of infrastructure, the newspaper report.
David Cameron has welcomed Johnson's announcement as "great news", hailing the Mayor of London as one of his "star players".