Theresa May is relaunching the Conservative election campaign amid fears Labour could soon take the lead in opinion polls.

Tougher sentences will be handed down to perpetrators of domestic violence against children under plans being set out by the Prime Minister to tackle the "hidden scandal".

It comes after a Tory source told The Daily Mail: "We fully expect to fall behind Labour in a poll in the coming days. It will happen."

A clutch of polls has shown the Conservative lead over Labour shrinking, with one ORB poll for the Sunday Telegraph putting Ms May's party just six points ahead, and another by YouGov for the Sunday Times putting the gap at seven points.

Polls in the Sunday newspapers gave Tories leads of between six and 14 points.

General Election polls and projections: May 27

The surveys found support for Tories ranging between 43 per cent and 46 per cent and for Labour between 32 per cent and 38 per cent, with Liberal Democrats trailing on 7-9 per cent.

They follow an opinion poll slip after Ms May U-turned on proposals for a "dementia tax," with Tory peer Lord Francis Maude saying the manifesto launch "hadn't been a brilliant success".

He told BBC Radio 4's Today programme: "The general advice would be that if you're starting an election campaign 20 points ahead in the polls then you should be incredibly bland and generic and not say anything that might possibly upset anyone."

He added: "It hasn't been a brilliant success, I think it's fair to say.

"The important thing, I think for them now, is to get back to where they started and talk about the need for the right leader."

UK General Election 2017 Show all 47 1 /47 UK General Election 2017 UK General Election 2017 12 June 2017 British Prime Minister Theresa May leaves 10 Downing Street for the 1922 committee on June 12, 2017 in London, England. British Prime Minister Theresa May held her first cabinet meeting with her re-shuffled team today Getty Images UK General Election 2017 12 June 2017 DUP leader Arlene Foster stands alongside deputy leader Nigel Dodds as they hold a press conference at Stormont Castle as the Stormont assembly power sharing negotiations reconvene following the general election on June 12, 2017 in Belfast, Northern Ireland. Discussions between the DUP and the Conservative party are also continuing in the wake of the UK general election as Prime Minister Theresa May looks to form a government with the help of the Democratic Unionist parties ten Westminster seats. 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Asked if the U-turn had damaged Ms May's brand, Lord Maude replied: "Well I think if you were able to run this video over again, you wouldn't start it in this way, clearly.

"But is it catastrophic? No it's isn't.

"Because at the end of it, the election is a choice between two people who are potential Prime Ministers and that's a very stark choice. And the rest of the election campaign should be unrelentingly about that."

Under the Conservative proposals, a new Domestic Violence and Abuse Bill will create an aggravated offence allowing harsher punishments for cases involving children.

A new domestic violence watchdog will also be established to speak up for victims and hold the police and criminal justice system to account.

Prime Minister Theresa May delivers a speech (PA)

Ms May said: "The last seven years of Conservative government have delivered real steps towards tackling domestic violence - we are punishing more perpetrators, and helping more victims get refuge and justice.

"But we will launch a relentless drive to help survivors find justice and increase the number of successful prosecutions.

"This hidden scandal, that takes place every day in homes across Britain, must be tackled head on. And we must respond to the devastating and lifelong impact that domestic abuse has on children, who carry the effects into adulthood."

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Despite a downward trend, there are still around two million victims of domestic abuse every year, with huge regional variation in the police response.

There have been large rises in victim reporting in recent years, but estimates still suggest only a fifth of victims report their abuse.

The Tory plans would introduce a statutory definition for domestic violence, providing legal underpinning for everything in the new act.

Proposals for the new domestic violence regime were set out in the Tory manifesto, which also pledged support for victims to leave abusive partners and a review of funding for refuges.