Image copyright PA Image caption The prime minister is backing the Britain Stronger in Europe group

The EU referendum has moved up a gear as groups hoping to front the official In and Out campaigns made their pitch to be allowed to spend up to £7m.

Britain Stronger in Europe says it has the backing of five political parties and David Cameron to make the case for the UK's continued EU membership.

Grassroots Out, which is vying with Vote Leave to lead the Out campaign, has Nigel Farage among its backers.

The Electoral Commission is expected to make a decision by 14 April.

The watchdog can select one designated lead campaign for both the "Leave" and "Remain" sides ahead of the referendum on EU membership on 23 June.

The chosen campaigns will get access to a grant of up to £600,000, an overall spending limit of £7m, campaign broadcasts, free mailshots and free access to meeting rooms.

It will judge each applicant's merits on the basis of a range of criteria, such as level of cross-party support, campaign tactics and organisational capacity.

'Every corner'

Britain Stronger in Europe is expected to be the only group seeking the formal In designation.

In its submission, it says it has the support of Labour, the Liberal Democrats, Plaid Cymru and three Northern Ireland parties - the Alliance Party, the Green Party and the SDLP.

Mr Cameron, who has become the overall figurehead of the In campaign, says he fully backs the application, saying it draws support from "every corner of the UK" and that its opponents are "divided into at least two camps who can't agree on very much".

While it backs staying in the EU, the SNP is running its own separate campaign in Scotland, while the Green Party of England and Wales has affiliated itself to Another Europe Is Possible - a different group formed by grassroots campaigners and Labour MPs on the left of the party.

The Grassroots Out application will be submitted by Mr Farage and Tory MPs Peter Bone and Tom Pursglove. It says it has the support of Tory, Labour, UKIP and DUP politicians.

Vote Leave, which is vying with Grassroots Out, has also submitted its application.

It said key individuals backing Britain Stronger in Europe were past supporters of joining the euro while several organisations supporting the campaign group received EU funding.

Political parties and other groups can run their own campaigns but they will be limited to a spend of £700,000 if they register with the watchdog and will have to report the source of donations.

If they don't register with the Commission they will be limited to spending less than £10,000.