Post offices are increasingly under threat of closure, the Liberal Democrats have claimed.

Figures released by the party on Thursday revealed that more than 57 per cent of all parliamentary constituencies could lose five or more of their post office branches.

The party has examined the closure of urban and rural branches based on numbers disclosed by David Mills, chief executive of the Post Office.

The party also highlighted a report commissioned by the National Federation of Sub-postmasters which found deprived urban areas rely on their post offices and see them as a vital part of the community.

The Post Office is planning to close around 3000 of its 9005 shops as part of a massive cost-cutting plan which is promoted as a re-invention programme.

Vincent Cable, the Liberal Democrat DTI spokesman, said the figures showed the potentially devastating impact of the programme which he condemned as "a complete fantasy".

"The Post Office network forms the hub of the local community - in some areas they are the only remaining retail outlet - and must be protected," he said.

"The government remains strangely silent, despite being the principal shareholder of the Post Office, and is oblivious to the needs and wishes of its stakeholders."

Cable argued that people on low incomes would be forced to open bank accounts and high street lenders have a poor record in helping them.

"The needs of the most vulnerable groups are not being addressed in the decision making process at all."