Downing Street has urged MPs to be cautious when responding to unsolicited messages, after the “spear-phishing” attack that targeted more than a dozen MPs, staff and journalists working in Westminster. Number 10 issued the warning on Monday morning, days after two police forces launched an investigation into what is being described as an attempted “honeytrap”. The message came as pressure builds on the Conservatives to take disciplinary action against the Tory MP William Wragg, who has admitted passing on the numbers of colleagues to a man he met on the dating app Grindr. The prime minister’s spokesperson said on Monday: “Anybody who has been targeted illegally should approach relevant authorities. It’s clearly important for anyone in public life to be sceptical of unsolicited communications.” Downing Street would not comment on suggestions that the messages could have formed part of an attempt by a foreign country to gain compromising material on British politicians. UK officials are, however, playing down such suggestions so far. The spokesperson said: “There’s a police investigation into this matter specifically but … we take threats to our democracy seriously.” More than 12 people are believed to have been targeted in the attack, in which they were sent messages from an unknown sender identifying themselves either as “Abi” or “Charlie”. The person sent messages that suggested they had previously met the recipient, such as saying the pair had previously had a “flirty conversation” either at party conference or in a bar in Westminster. In several cases they then sent an explicit picture. Several people came forward over the weekend to describe their experience of having been targeted by the campaign. Tory backbencher Andrea Jenkyns said she had received messages that referred to a previous meeting at the party’s annual conference, which she had reported to the whips. Luke Evans, another Conservative MP, said he had reported similar messages to the police. Harry Yorke, a journalist at the Sunday Times, said he had received flirtatious messages by an unknown woman called Charlie. Both Leicestershire police and the Metropolitan police said they had opened investigations into the incidents. Scotland Yard said in a statement on Friday: “Officers from the Met’s parliamentary and diplomatic protection command are carrying out an investigation following reports that a number of unsolicited messages were sent to MPs over recent months.” Meanwhile the Conservatives are facing pressure to take action against Wragg, who admitted last week that he had given the personal numbers of some of his colleagues to a man he met on Grindr. He said he had sent the man photographs of himself and feared what he would do with them if he did not comply. Jenkyns tweeted on Sunday: “It’s unforgivable of him to compromise the security of fellow MPs. Action is needed.” So far, however, the government is standing by Wragg. Jeremy Hunt, the chancellor, last week called his admission and apology “courageous and fulsome”.