The BBC's Emma Udwin: "Supporters are impatient for a more pro-active campaign"

Britain in Europe is the biggest of the pro-euro groups and is likely to become the principal focus of efforts to sway the British public in favour of the single currency.

The government has promised to hold a referendum before taking a decision on whether or not to join the euro. The currency officially launched on 1 January this year, but the UK has so far exercised its right to "opt out".

The meeting in Birmingham marks the start of a euro information drive that will travel to 125 towns and cities across the UK over the next few months.

Eurosceptics were also making their views known on Saturday, with Tory former minister Michael Portillo sharing a platform with Labour peer Lord Shore at a Campaign for an Independent Britain conference.

'Britain is losing out'

Head of British Airways, Lord Marshall, who is launching the Britain in Europe group, said the programme is designed to fight "the culture of misinformation" surrounding the euro.

"The facts are that the single currency has now been successfully launched and Britain is losing out, because we are staying out," he said.

The euro debate is likely to heat up considerably in the run up to June's European Parliament elections as parties use the poll to focus on arguments for and against joining.

Eurosceptic headstart

Britain in Europe has made a later start than many of its eurosceptic opponents, most notably millionaire Paul Sykes' Democracy Movement.

It has led to criticism that the group will be forced to spend as much time rebutting what the eurosceptics have said as it does putting its own case across.

Portillo: 'Euro would mean higher taxes'

The main reason for this appears to be that prominent Tory pro-Europeans are reluctant to speak out against the Conservative party's official line before the June elections.

Tories have effectively ruled out joining the euro for the foreseeable future.

Mr Portillo said joining the euro would result in higher taxes and unemployment in Britain.

He told BBC Radio 4's Today programme: "It's just like when we were in the exchange rate mechanism.

"If you have got to have one interest rate and one exchange rate for all of Europe, it can't possibly be right.

"If you have taken away the ability for different movements in the economies to be reflected in exchange rates, then the only way in which pressure can be released is in higher unemployment."

Lord Shore is expected to attack the European Parliament for failing for so long to tackle corruption in the European Commission.