Mr Mugabe was expected to answer questions on a claim he made about huge-scale diamond theft at the eastern Marange mines.

But Temba Mliswa, who leads the parliamentary committee on mines, said the former president had not been officially informed of the summon.

He told Reuters: "It has been delayed but that resolution still stands... He will have to appear before the committee whether he likes it or not."

Mr Mugabe had accused foreign mining firms of "swindling" and "smuggling" in an interview on state-run TV in 2016.

"The companies have virtually robbed us of our wealth," he said, adding the treasury had seen little of about $15bn (£11bn) they had earned.

The 94-year-old has not commented on the summons to parliament.

He was forced to resign last December in the wake of a military takeover, and still has the privileges of a former head of state.

Timeline of the controversial Marange diamonds:

BBC In 2006, more than 20,000 illegal diggers descended on the Marange fields.

Reports followed of large-scale killings by Zimbabwe's security forces to stop the smuggling, prompting Marange diamonds to be banned in 2009.

A Panorama investigation found in 2011 that in the Marange fields, the police and military recruited civilians to illegally dig for diamonds for them.

In 2012 a campaign group said at least $2bn worth of diamonds had been stolen from the Marange fields. Partnership Africa Canada (PAC) said the "theft" had enriched Zimbabwean officials, international gem dealers and criminals.