Royal Mail staff shareholders are being asked to sell their stock to Czech billionaire Daniel Křetínský as his company begins lobbying investors to accept his offer to buy the postal firm.

The West Ham director made a formal submission of £3.57bn to parent company International Distribution Services (IDS) in May and it recommended that shareholders accepted his offer of 370p per share.

This is more than the 315p it is trading at and significantly higher than the 220p it was worth before Křetínský’s first offer to buy the company.

He already owns 27.5% of Royal Mail and he needs the approval of shareholders of three quarters of IDS to buy up the remaining 72.5%

However, the government has the ability to block the deal.

Shadow business secretary Jonathan Reynolds has written to Křetínský seeking assurances that Royal Mail will remain headquartered and tax-resident in the UK.

Reynolds also wants a commitment from him to work closely with the Communication Workers Union (CWU) to build a sustainable Royal Mail.

CWU general secretary Dave Ward said last month that the takeover bid was “a direct result of a failed and ideological privatisation over a decade ago mixed with the blatant mismanagement of the company in recent years”.

He added: “These events have ripened one of the most iconic and important companies in the UK for a takeover by foreign investors.

“We do welcome some of the commitments that have been made but the reality is postal workers across the UK have lost all faith in the senior management of Royal Mail and the service has been deliberately run down.”