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.
The committee will consider the petition at its meeting next week and decide whether to schedule a debate on it, Ms Jones said.
“That doesn’t mean that the committee will be deciding whether or not it agrees with the petition – just whether or not it should be debated.
“Any debate would allow a range of views to be expressed.”
The petition has more signatures than any other on the parliamentary website.
But a number of people on Twitter have pointed out that many people signing it appear to be doing so from outside the UK.
A House of Commons spokeswoman said the petition was created on 24 May. There were 22 signatures on it at the time the referendum result was announced. It has not been confirmed if it was set up by a Leave or Remain supporter.
The petition’s website states it was set up by an individual called William Oliver Healey, and says: “We the undersigned call upon HM Government to implement a rule that if the Remain or Leave vote is less than 60%, based on a turnout less than 75%, there should be another referendum.”
Thursday saw a 72.2% turnout, significantly higher than the 66.1% turnout at last year’s general election, but below the 75% mark suggested by Mr Healey as a threshold.
BBC political correspondent Iain Watson says the petition has attracted a lot of attention but has zero chance of being enacted, because it is asking for retrospective legislation.
Our correspondent says some referendums do have thresholds but those clauses must be inserted in legislation before the vote so everyone is clear about the rules.
You can’t simply invent new hurdles if you are on the losing side, our correspondent says.
Mr Cameron said on Friday he would stand down as prime minister by October following the leave result.