No 10 to fly saltire as three party leaders miss PMQs to campaign against independence before referendum

The three Westminster party leaders have made the drastic decision to travel to Scotland on Wednesday to campaign against independence and will not attend prime minister's questions.

The emergency move throwing aside all previous plans was agreed on Monday afternoon at a meeting between Ed Miliband and David Cameron. In a joint statement issued with Nick Clegg they said: "There is a lot that divides us – but there's one thing on which we agree passionately: the United Kingdom is better together.

"That's why all of us are agreed the right place for us to be tomorrow is in Scotland, not at prime minister's questions in Westminster.

"We want to be listening and talking to voters about the huge choice they face. Our message to the Scottish people will be simple: we want you to stay."

Prime minister's questions will go ahead but with understudies William Hague and Harriet Harman.

The agreement by the party leaders not to attend PMQs follows intense criticism of Cameron for not planning to go to Scotland until next week. He had been advised that his presence would be a negative influence, but a mixture of his own desperation at the prospect of losing the union and the belief that something drastic was needed to revitalise the no campaign changed his thinking.

Miliband and Cameron made their decision in the knowledge that one poll had suddenly put the yes campaign ahead, and another was about to be published confirming the trend showing the two campaigns were neck and neck.

They also discussed the decision of Gordon Brown, the former prime minister, to rush ahead with a package and timetable for further devolution.

There was an agreement that the no campaign had no time to lose and needed to get back on the front foot before there was a landslide rushing to the yes campaign on a wave of patriotic emotion.

Cameron said: "We have our own ways separately of talking about why we are better together, but I am sure one thing we will say is that it is a matter for people in Scotland, but we all want you to stay."

He sidestepped questions about his own future saying: "I do really care about this issue, I care passionately about the United Kingdom and I want to do everything I can to put the arguments in front of the people. In the end it is for the Scottish people to decide but I want them to know, and I speak as the prime minister, that we want you to stay."

Miliband's office stressed that three party leaders would not be campaigning together or travelling to Scotland together.

Clegg, the deputy prime minister, said the overall long-term aim was to form a radically decentralised British state, but he rejected calls from Graham Allen, the chair of the political and constitutional reform select committee, to symbolise the three parties' commitment to Scottish devolution by appearing on a joint platform in Scotland.

He also denied that the timetable for Scottish devolution was a panic move or a last-minute effort to cobble together a cross-party deal on devolution. He said the breakthrough had actually occurred in early August when the three party leaders had agreed a joint statement on "an irreversible process of reform" in Scotland. He said the latest statement about a timetable was "all about the means of delivering a commitment that was made".

In a further symbolic move, Cameron has decided to fly the Scottish flag above No 10 and other Whitehall buildings until the referendum takes place.

This will be a "clear message" to Scotland that the rest of the UK wants the country to stay in the union, the prime minister's spokesman said.

He added: "One of the things cabinet discussed this morning is that there is nothing more important than the future of the United Kingdom and the future of Scotland in the coming days. The prime minister has been very clear in his message that we want you to stay and I would put the flying of the saltire over No 10 firmly in that context."

Cameron's spokesman denied that this was a patronising or trivial move, pointing out that the saltire has flown over No 10 on previous occasions, including St Andrew's Day. In the past, Cameron has said Britain does not "do flags on the front lawn".

It is understood the prime minister will return to Westminster after the visit before going to Scotland for a second time next week.