Liam Byrne was welcomed as part of a “West Midlands mafia” when he made his debut appearance as Gordon Brown’s Cabinet co-ordinator in the House of Commons.

The MP for Birmingham Hodge Hill answered questions in his new role as head of the Cabinet Office and Chancellor of the Duchy of Lancaster.

He is to oversee the co-ordination of Government policy across departments in the new position, which has been dubbed Mr Brown’s Cabinet “fixer”.

But Mr Byrne was also mocked by Conservatives for failing to make it into the Cabinet himself.

The job he is now doing has previously been a Cabinet position and his predecessor in the role, Ed Miliband, was a full member.

However, when Mr Byrne was promoted last week, he was told he will simply be allowed to attend Cabinet meetings rather than being a member of it.

The MP, previously the Minister responsible for Immigration, now leads a team which includes West Bromwich West MP Tom Watson.

He was welcomed to his new role by Conservative MP Andrew MacKay (Bracknell), who briefly represented the now-defunct constituency of Birmingham Stechford in the 1970s.

Mr MacKay, referring to Mr Watson and other West Midlands MPs with ministerial roles, including Home Secretary Jacqui Smith (Redditch), Treasury Minister Ian Pearson (Dudley South) and senior Business Minister Pat McFadden (Lab Wolverhampton South West), who will represent his department in the Commons, said he was delighted to see a “West Midlands mafia” in the Government.

And the theme was taken up by one of Mr Byrne’s Cabinet Office ministers, Cardiff West MP Kevin Brennan, who quipped: “It makes a welcome change from the Celtic mafia.”

But Conservative spokesman Nick Hurd told Mr Byrne: “May I add my voice of congratulations to the new ministerial team, and indeed commiserate with the Chancellor of the Duchy of Lancaster for assuming that grand office at the very moment it is demoted from Cabinet.”

He asked Mr Byrne to comment on fears that even more post offices could close if the Government gives the contract to operate the post office card account, used by millions of pensioners and benefit claimants to claim payments, is awarded to a rival operator.

The contract to operate the card is currently held by the Royal Mail, Post Office Ltd’s parent company, but a decision on who wins the tender to run the successor to the card is due within weeks.

It was announced earlier this year that 55 post offices in Birmingham, Warwickshire and Solihull are to close, including five which are to be replaced by part-time “outreach” services, and 69 in the Black the Black Country, Worcestershire and Herefordshire are threatened with the axe.

Mr Byrne said the Government was currently subsidising the Post Office network by £150 million a year.

He said: “Three and a half million pounds a week in subsidy is not sustainable. We need to make changes.”

Post Office Ltd recently completed a consulation on closures in Herefordshire, Worcestershire and across the Black Country, and is expected to announce its decision around the end of the month.

Earlier this year, the company consulted on the potential closure of 26 post offices in Birmingham, but only one was saved.

Mr Byrne’s exclusion from the Cabinet was a surprise move in Gordon Brown’s reshuffle last week. He has been appointed to the Pricy Council, meaning he formally becomes the Right Honourable Liam Byrne in the same way as a full member of the Cabinet.