A ballot of BT employees over pay has been cancelled following legal advice.

The Communication Workers Union (CWU) has cancelled the notice for the industrial action ballot after lawyers warned that there were technical breaches that could have invalidated the ballot.

It has not been revealed precisely why the ballot may have broken Britain’s trade union legislation.

The CWU held the ballot after rejecting the original offer from BT of a 2% pay increase, asking for a 5% increase.

A national strike would be the first for the company since 1987 and would see more than half of BT’s staff walkout.

The CWU will reopen negotiations with BT and will take necessary steps to allow a re-ballot if negotiations are unsuccessful.

Andy Kerr, CWU deputy general secretary, said: “We're bitterly disappointed that this ballot has had to be cancelled. It's devastating for our members and for trade union rights in the UK and of course it doesn't help to resolve the outstanding issues over pay which we have with BT.

“The legal technicalities on which this ballot has been cancelled again raise questions over the right to strike and the extremely restrictive trade union laws that exist in the UK. The law, in our view, appears to be outdated when it comes to the provision of information.

“We will take all necessary steps to allow us to re-ballot our members as soon as is practically possible. In the meantime we will also be taking up an offer from BT for a meeting to see if there is a way to resolve this dispute without the need for industrial action.”

A BT spokesperson said: “BT is pleased that the CWU has withdrawn its ballot for industrial action. There were procedural issues regarding the ballot that we raised from the start and the union have now accepted this to be the case.

“Our door remains fully open to the union and so we hope we can sit down and resolve this matter. An amicable agreement is in everyone’s interest and the withdrawal of the ballot provides both sides with a window of opportunity in which to reach such an agreement.”

Read more articles on pay and bonuses