Andy Burnham hailed yesterday as the 'best day of my life' as he opened a temporary 'No10 North' office in Manchester.

The Prime Minister praised the project after flying in on a Government jet for 38 minutes from Scotland, where he attended the Commonwealth Games' opening on Thursday night.

He dismissed fears about the bill facing taxpayers for the 'gimmick' and huge security operation, saying: 'What does it cost for everybody to troop down to London every time there's a meeting when you need to make an argument about something?'

He posed in front of a fake No10 door with Cabinet Office minister Louise Haigh, Cabinet Secretary Dame Antonia Romeo and Chancellor John Healey.

Mr Burnham is making great play of his decision to be based part of the week in Manchester, where his family lives and he used to be mayor.

The so-called 'King of the North' wants to use the arrangements as a symbol of his drive to devolve power out of Westminster.

However, construction has not even started yet on the site earmarked to become the PM's base in the city, and it will not be operational until 2032.

Instead, Mr Burnham is using Heron House, a Government office in the centre that is used by GCHQ, a pub and a register office – a bridal party was seen going in yesterday.

Security at the building has been hugely increased and workers have been busily sprucing up nearby Albert Square.

No10 has insisted there will be no extra costs to the taxpayer, but experts have warned that the bill for fortifying an office for the PM and providing round-the-clock armed police will be eye-watering. Downing Street and much of the Government estate in Whitehall is closed off to the public.

Addressing staff at the Manchester office yesterday, Mr Burnham said: 'I cannot tell you what a proud moment this is. I think this might be the best day of my life.

'I'm not joking. I know you think I am, but I'm not. Things are just completely coming full circle here, for me to be here with you all in the heart of Manchester this Friday morning at the end of a fairly big week is just everything to me.

'Because it's almost exactly 35 years since I left this city as a recently graduated young man, couldn't find a job in the city. 

'It was in a pretty bad place at that time, it's fair to say. The 80s turned into the 90s. There wasn't much.

'And that really is an experience that I've never forgotten. My generation of people growing up here, and it's true of places all over the country, to get on in life you had to leave where you were because things weren't here.'

He added that No10 North was an example of 'putting power in every postcode so that people can turn things around for themselves and make changes just as this great city has done and the other English cities are doing through devolution.'

The Treasury approved the 'outline case' for a civil service 'digital campus' in Manchester in March this year, after being in development since the council acquired the disused retail park in 2017.

That is now envisaged as the permanent No10 North.

Construction is due to begin at the five-acre site over the coming years but the 'target' for it becoming operational is not until 2032 – three years after the latest date for the next general election.

This week the PM's spokesman said: 'The running of No10 North will be covered by existing Cabinet Office budgets. There is no additional cost to taxpayers.'