EU referendum: Leave's 'register to vote' website sparks row
Remain campaigners have accused their Leave opponents of potentially "misleading" people wanting to register online to vote in the EU referendum.
They say a Vote Leave website appears to offer people the chance to register but in fact only records their details for the Vote Leave campaign.
Education Secretary Nicky Morgan has written to the Electoral Commission warning of "underhand tactics".
The watchdog said it did not regulate the content of campaigner websites.
Vote Leave have been contacted by the BBC but have yet to comment on the row, which comes ahead of the deadline to register to vote on Tuesday.
The Vote Leave web page asked users to enter their personal details, including their address, and click a "Register To Vote Now" button.
By clicking the button, it suggested people would "find all the information they need" about voting and be "on the way to registration". The result, though, was a page thanking them for signing up to support the campaign itself.
This later changed, with users directed to a generic page about how to register, including a link to the official www.gov.uk website.
But the Britain Stronger in Europe campaign group suggested their opponents may have "manipulated" online advertising listings in an attempt to mislead voters.
Ms Morgan and Labour MP Stella Creasy have written to the watchdog calling for an urgent investigation into whether this was a breach of the code of practice on data, which is overseen by the Information Commissioner.
"It has come to our attention that Vote Leave appear to have paid for online advertising to ensure that their campaign website regarding registration is promoted ahead of the government website that directly enables citizens to register to vote," they wrote.
"This website does not enable people to register, and therefore could easily mislead people in to thinking that they have secured their ballot paper.
"By securing a ranking for this site higher than the official registration site, Vote Leave's underhand tactics could disenfranchise citizens without their knowledge who have in good faith used this site to try to register."
In a statement, the Electoral Commission said it did not have the remit to investigate and said anyone who was not registered to vote should do so online by the 23.59 BST deadline on Tuesday 7 June.