PRIME Minister David Cameron has criticised Alex Salmond for waving a saltire behind him as Andy Murray celebrated winning Wimbledon.

Downing Street sources said the Conservative leader thought the move "didn't feel right" and that it was a "day for sport, not politics".

They also suggested there would have been uproar if the Prime Minister had unfurled a Union flag behind the First Minister's head.

Mr Salmond has defended waving the flag after Murray's win, saying he had no idea he would be seated behind Mr Cameron and his gesture had nothing to do with politics.

Despite strict rules banning the waving of large flags, Mr Salmond also said the Wimbledon authorities had been understanding about his gesture.

It is understood Mr Cameron also intends to step up his Government's campaign against independence by ordering his ministers and Tory MPs to make the case for the Union in England.

The Prime Minister hopes that the "lovebombing" from England will help convince Scots of the desire from other parts of the UK for them to stay.

A source close to Mr Cameron admitted not everyone in England was persuaded that Scotland should remain part of the UK.

He said: "There will always be little Englanders, Nigel Farage types. But you don't have to scrape far beneath the surface to find a love for Scotland."

Before the last Quebec independence referendum in 1995, the Canadian Government organised rallies designed to persuade people there that other Canadians did not want them to leave.

They attracted huge support and are credited by many with having a significant impact in what was a close result.

Mr Cameron is also understood to want a decisive win in next year's referendum, believing such a result would settle the issue for a long time.

He is also thought to believe there is a need to balance the negative and the positive in the pro-Union campaign.

The SNP seized on reports last month that some within the No campaign, Better Together, refer to their organisation as Project Fear.