A proposed law designed to "protect genuine heroes" by prosecuting people wearing military medals they have not earned has passed its first Commons test.

Conservative Gareth Johnson (Dartford) labelled the practice "insulting" and said he wants to target "Walter Mitty" characters who pretend to be something they are not by reintroducing legislation making it a criminal offence.

MPs approved his Awards for Valour (Protection) Bill at second reading, with the chances of his proposal becoming law increased after both Labour and the Government supported the idea.

Legislation making the unauthorised wearing of medals a criminal offence was originally introduced in the aftermath of the First World War by the then secretary for war, Winston Churchill.

It remained on the statute book until 2006 when the new Armed Forces Act came into force and the provisions relating to military decorations were not carried over.

In the absence of any deterrent, Mr Johnson said there was mounting anecdotal evidence that more people were wearing medals they had not earned.

Conservative Philip Davies (Shipley) labelled the Bill as worthy but also an example of "gesture politics", warning it could have unintended consequences for veterans and people with mental health conditions.

Mr Johnson's proposal will undergo further scrutiny at committee stage at a later date.

Speaking during the Bill's second reading in the Commons, Mr Johnson said: "To undermine our veterans is wrong. To claim you're a military hero when you are not is wrong, and to steal valour is wrong.

"The point of this Bill is to protect genuine heroes. People should not be able to claim that they are heroes when they are not.

"The so-called Walter Mittys, parading themselves at remembrance service parades and elsewhere, sporting medals they have not earned, is not only insulting, but it undermines those veterans who have legitimately earned them."

Mr Johnson, who showed MPs his great-grandfather's military medal, said the new legislation would not stop family members from wearing medals their relatives had earned.

He also said the Bill would be sensitive to those with mental health issues, as well as those who suffered "wardrobe malfunctions", with tradition dictating that all medals that had been earned should be worn on the left breast.

Mr Johnson added: "What I want to do is to make sure we catch only those who intend deliberately to deceive others."

Tory Bob Stewart, a former British Army officer, also warned of people wearing SAS berets, saying he thought only one in 20 of those he had seen wearing berets had actually served.

He said: "It's astonishing, the number of people who have been in the Special Air Service in this country."

Mr Davies, while opposing the Bill, said the idea was "admirable" and it should be an "absolute priority" to help veterans.

He went on: "But unfortunately I don't see this Bill as either being necessary or actually helpful, and I'm most concerned it will disproportionately affect people with mental health issues and even veterans themselves, which would be a very unfortunate, unintended consequence of a laudable aim."

Defence minister Harriett Baldwin said: "This dishonest behaviour we've heard about today ... is not harmless fun or mindless eccentricity.

"In actual fact its implications are much worse and its ramifications are far graver than many would appreciate at first glance - all the more so when it involves the unauthorised wearing of decorations and medals.

"Firstly, because it is a gross affront to those who have genuinely served their country at considerable risk to themselves and who, as is intended, wear their medals with great pride."

She added: "Wearing unauthorised medals is harmful because it undermines the integrity of our formal military honours system."

Mr Davies questioned why the Government did not support the same measures proposed in an e-petition earlier this year.

Ms Baldwin replied: "(Defence Secretary Sir Michael Fallon) has been thoroughly convinced by the excellent case by (Mr Johnson)."

Mr Davies laughed at the answer.