Thousands of postal workers are to vote on strikes in a row over post office closures, job cuts and pensions.

The Communication Workers Union has served notice that around 3,500 of its members in Crown offices, supply chain depots and administration sites across the UK will be balloted in the coming weeks on whether to launch a campaign of industrial action.

It is the first time workers from the different parts of the business have been balloted together, with the result due on August 19.

The union said the ballot was in protest at the company's plans for 'wholesale privatisation' of the Crown network, job losses and the closure of the defined benefit pension scheme.

CWU general secretary Dave Ward said: 'The Post Office as we know it is on the brink of extinction. It is clear that the board's plan is one of closure, redundancy and cost-cutting on an epic scale which will permanently undermine this great British institution.

'We are repeating our call for the board to resign with immediate effect and be replaced with people who are actually interested in delivering jobs and services through this iconic brand.

'We will be highlighting our concerns for the Post Office with new Business Secretary Greg Clark, following up the delivery of our 20ft postcard to his office last week.

'The Government's response on funding has been wanting and misleading - money has been spent on closing down offices and paying off staff instead of bringing new business into the network. The lack of imagination and ambition for this great British institution is staggering.

'We are left with no choice but to take strike action to defend the jobs and pensions of our members and the services they provide.'

The Post Office said it was disappointed by the CWU's decision to ballot for strike action and called for talks.

A statement said: 'The Post Office is committed to maintaining the vital services offered by its branches at the heart of communities across the UK, with 99% of the UK's population within three miles of a Post Office branch. However, this level of service can only be secured for future generations by ensuring the business's financial sustainability.

'The Post Office operates in a fast-changing and highly-competitive environment which has meant significant changes to the organisation and the way that it works. It understands that some of these changes are difficult for those affected by them and is committed to treating people with dignity and respect.'

Kevin Gilliland, Post Office network and sales director, said: 'We've made steady progress in making our business simpler to run, reducing costs to the taxpayer whilst at the same time modernising our network which provides essential services to communities throughout the UK. We are making it better for customers, providing unprecedented ease of access to our services through longer opening hours. We're now the largest retailer open on Sundays, with 3,800 of our branches open seven days a week.

'All of our proposals are taken forward with the utmost care for the people they affect and we're proud of our track record in supporting people through difficult changes.

'We will give serious consideration to any ideas that the CWU put forward to help us create the Post Office network our customers need for the future and urge them to work in partnership with us to secure the future of our services.'

The union said there had been 2,000 job losses this year, with 60 Crown offices set to be franchised, 16 moved into another retailer and four closing.

The closure of the defined benefit pension scheme will leave thousands of staff worse off in retirement, said the union.