CWU general secretary Dave Ward has warned the Royal Mail takeover bid is “not right for our members, this is not right for the country.”

He addressed 4,500 CWU members in an online video after the owner of the privatised service welcomed an improved £3.5 billion takeover offer from Czech billionaire Daniel Kretinsky.

Mr Ward urged them to show a united front as CWU will have a “big influence” on the upcoming political and industrial negotiations over the future of postal services in Britain.

He said the union has been engaging with Labour on a customer and worker-led alternative model of ownership for the historic institution and that the government also faces a “dilemma” as it reviews the potential buy-out under the National Security Act.

Mr Kretinsky already owns 27.5 per cent of Royal Mail’s parent company International Distribution Services (IDS) through his equity investment vehicle Vesa.

“Essentially, our view is this is not right that this should be sold entirely to Vesa, we don’t believe that is right for our members, we don’t believe that’s right for the country,” Mr Ward said, saying it “equally” doesn’t support the current Royal Mail board of directors’ vision for growth.

He said with a general election coming up renationalisation will be “difficult” to achieve, but “there are other business models that range from things like mutuals, not-for-profits, public benefit companies that we have already been exploring with the Labour Party.

“We will have a big influence over what’s going to happen,” he said.

IDS on Wednesday said that Mr Kretinsky’s EP Group had agreed to offer a set of “contractual undertakings,” including commitments to maintain six-day-a-week first-class letter deliveries under the universal service obligation, though leaving daily second-class deliveries at risk.