LABOUR must “robustly scrutinise the detail” of Royal Mail’s takeover offer by Czech billionaire Daniel Kretinsky, Communication Workers Union (CWU) said today.

General secretary Dave Ward’s call came after it emerged the £5 billion bid will undergo a government probe, including into potential links with Russia.

“The contractual obligations negotiated between the failed current Royal Mail Board and Mr Kretinsky are not strong enough to protect workers, customers and the crucial infrastructure that Royal Mail provides for our communities and the economy,” he added.

“It’s time for a new business and ownership model which gives workers a greater say over the future direction of the company.”

The purchase of the postal service’s parent company has been “called in” by officials for an investigation under the National Security and Investment Act.

The bid will be suspended as is routine with the potential for government to block it.

There is no indication that Mr Kretinsky, who has not commented, has walked away from the deal.

A similar review when he increased his stake in Royal Mail found nothing but it is thought this probe will be more thorough as he is trying to buy the whole parent company, including assumed debts, as opposed to a stake.

Mr Kretinsky's companies own a gas transmission business called EUStream that carries Russian gas into Europe.

This is with the knowledge and permission of the European Union and none of Mr Kretinsky's companies buy or trade in Russian gas, which has been subject to US and EU sanctions since the invasion of Ukraine.

Officials will look at whether Britain could be hurt by the private purchase of a postal service.

The probe will be run by the Cabinet Office with input from the Department for Business and Trade.

Mr Kretinsky has said he would never walk away from Royal Mail’s commitment to deliver letters across Britain six days a week — the Universal Service Obligation (USO).

In writing however he has only committed to honouring this for five years.

He previously said he is “very open” to profit sharing but that the shared ownership the union is pushing for “creates a lot of complexity.

“For instance, what happens if the employee leaves? He has shares, he is leaving, he is not working for the company, he needs remunerating.”

Mr Kretinsky has also guaranteed no compulsory redundancies or changes in terms and conditions, but only until 2025.