The Derry & Strabane District Commander Gordon McCalmont has said the PSNI is investigating a complaint from Colum Eastwood about a 'fake letter' posted through letter boxes locally in the run up to Thursday's election.
The top police officer confirmed: "Police received a report just after 11.30 a.m. today (Tuesday, December 10) about a letter circulating in the Foyle area in relation to the up and coming election.
"Enquiries are underway, and we are liaising with our colleagues in the Electoral Office.
"I would appeal to anyone who has information about this letter, or who is in receipt of such a document, to call us on 101 and quote reference number 688 of 10/12/19."
The Derry commander issued the confirmation after Mr. Eastwood complained that letters were delivered to homes with the false claim that they had emanated from his election campaign.
The matter has now been reported to the PSNI and the Electoral Commission, the SDLP said.
"I am disgusted that fake letters purporting to be from me have been delivered to houses in Derry," said Mr. Eastwood.
"Let me be clear, these letters are not from me nor are they from anyone associated with my campaign. This is an organised attempt to lie to the people of Derry, to poison our democratic process and those responsible should be ashamed.
"The people of Foyle know that this is a close race between myself and Elisha McCallion. Voters should make up their minds on our records, not a campaign of dirty tricks," he added.
The SDLP leader said the party's main rival in this campaign, Sinn Féin, should condemn what he described as "vicious lies" contained in the letter.
“My team and I are running a positive campaign, focusing on how we can invest in Derry, make our communities a better place and work with others to stop Brexit.
"I made it clear weeks ago that the SDLP will engage in a clean campaign and I would take strong action if anyone was suspected of nasty personal attacks. That has been our approach to this whole campaign and it is disappointing others have not followed suit."
Meanwhile, the party said the letters which have been "falsely circulated in Colum Eastwood’s name amount, in our view, to a breach of electoral law".
"The SDLP has referred this matter to the Electoral Commission and to the PSNI for investigation," the party added.