Geoffrey Cox has said the Conservative Party chief whip, Mark Spencer, gave him permission to visit the British Virgin Islands to conduct his second job during the pandemic.
The former attorney general is under-fire after it emerged he took part in Commons votes remotely from British Virgin Islands (BVI).
He has earned hundreds of thousands of pounds advising the territory on a corruption probe launched by the Foreign Office.
In a statement issued on Wednesday, Cox said it had made “no difference” whether he was in the UK or not as face-to-face meetings were advised against due to Covid.
Cox added he had “consulted the chief whip specifically on this issue and was advised that it was appropriate”.
Parliament introduced a proxy voting system during the pandemic to allow MPs to take part without having to physically be in the building.
Cox has also been accused of breaching parliamentary rules by giving out legal advice to the BVI while sitting in his Commons office in London.
Deputy Labour leader Angela Rayner said the alleged use of the office appeared to be “an egregious, brazen breach of the rules” and has written to standards commissioner Kathryn Stone requesting a formal investigation.
“A Conservative MP using a taxpayer funded office in parliament to work for a tax haven facing allegations of corruption is a slap in the face and an insult to British taxpayers,” she said.
Cox said he would “fully cooperate” with any investigation but did “not believe that he breached the rules”.
The row over second jobs comes in the wake of a recommendation that Owen Paterson should be suspended for six weeks after he broke the ban on paid lobbying by MPs.
In the bitter aftermath of the row, Paterson announced he was quitting as MP for North Shropshire after 24 years, as an attempt by the government to delay his punishment by ripping up the current standards system failed when opposition parties refused to offer their support.