The House of Commons petitions committee has said it is investigating allegations of fraud in connection with a petition calling for a second EU referendum.
Any signatures found to be fraudulent would be removed, it said.
More than 3.1 million people have signed the petition, although PM David Cameron has previously said there will be no second referendum.
It comes after the UK voted 52-48 to leave the EU in Thursday’s referendum.
Helen Jones, who chairs the cross-party petitions committee, said in a statement posted on Twitter that it was taking the allegations of fraud “very seriously”.
“People adding fraudulent signatures to this petition should know that they undermine the cause they pretend to support,” she said.