LONDON (Reuters) - Britain s democracy is one of the most secure in the world and will remain so, a spokesman for Prime Minister Theresa May said on Monday in response to a question about a suggestion that there may have been foreign interference in the Brexit vote. Opposition lawmaker Ben Bradshaw last week urged the government to look into reports by advocacy group Open Democracy suggesting that the origin of some Brexit campaign funds was unclear. Bradshaw said in parliament the issue should be investigated  given the widespread concern over foreign and particularly Russian interference in Western democracies . At a briefing with reporters, May s spokesman was asked if the prime minister was concerned about the reports.  I am not aware of those concerns,  he said.  More broadly, as we ve always said, the UK democratic system is amongst one of the most secure in the world and will continue to be so.  Open Democracy, which describes itself as an independent media platform aiming to challenge power and encourage debate, had raised questions about the finances of businessman Arron Banks, one of the main financial backers of the Brexit cause.  The only people concerned are those that still can t come to terms with the fact that they lost the referendum so will come up with more and more ludicrous excuses,  Banks said in a statement texted to Reuters by a spokesman. Banks dismissed Open Democracy s report without addressing it in detail and accused Bradshaw of peddling a  tedious myth  about Russian meddling in the Brexit debate. The Electoral Commission, which regulates political finance in Britain, said in April it was investigating campaign spending by Leave.EU, one of the pro-Brexit organizations funded by Banks. It gave no details of what its probe was about.  I m not remotely worried. We did nothing wrong,  Banks said in the text. A spokeswoman for the Electoral Commission said the investigation was still going on and it would not provide any further information until it was complete. Open Democracy had also raised concerns about a large donation to Northern Ireland s Democratic Unionist Party (DUP), which is now propping up May s minority Conservative government. Open Democracy said the origin of the money, which was spent on campaigning for Brexit, was unclear.  The DUP, which was earlier reported to have said the funds came from  an organization in England that wants to see the union (between the UK s constituent parts) kept , did not respond to repeated requests for comment. During a debate in parliament later on Monday, May was asked whether EU leaders had discussed the issue of Russian interference at a summit last week. She said it had not come up. 