More than 100,000 former and current Royal Mail staff will this week be asked to sell their shares to a Czech billionaire.

On Wednesday morning, Daniel Kretinsky’s investment group, which wants to buy Royal Mail’s parent company, will publish its formal offer online and send it by post.

Mr Kretinsky can then formally start lobbying investors to accept the offer.

He needs the approval of shareholders of three quarters of the parent company, but this task will be made easier because he already owns 27.5% of it.

Big asset managers including Blackrock, UBS, Vanguard and Schroders own most of the other 72.5% of International Distribution Services (IDS) that Mr Kretinsky does not own.

Meanwhile, Royal Mail staff still collectively own 5.5% of the shares after qualifying staff received 600 shares in the company at the time of its privatisation in 2013.

Mr Kretinsky made his fortune in energy companies. He also has stakes in Sainsbury’s and West Ham Football Club.

The board of IDS has already recommended that shareholders big and small accept his offer of 370p per share.

This is more than the 319p it is currently trading at and substantially above the 220p it was worth before Mr Kretinsky’s first offer to buy the company.

However, the government still has the ability to block this deal, which it may do given Royal Mail’s importance to the UK.

Mr Kretinsky’s EP Group has offered a series of time limited guarantees including the retention of the Royal Mail logo, its UK headquarters, and its UK tax base.

It also offered to honour current employment agreements with unions and promised not to split off the profitable parcels business, which IDS also owns.

Chancellor Jeremy Hunt has said that the deal would be subject to the normal scrutiny but he was not opposed “in principle”.

Shadow Business Secretary Jonathan Reynolds has written to Mr Kretinsky to seek assurances that Royal Mail will remain headquartered and tax-resident in the UK.

My Reynolds also wants a commitment from Mr Kretinsky to “work closely with the Communication Workers Union (CWU) to build a sustainable Royal Mail”.

The CWU is pushing for “a new ownership and governance model that builds a postal service for the workers and customers”.

Sources close to Mr Kretinsky said that they would consider a model which involved some employee ownership or participation.