A Labour frontbencher has defended a social media post used by the party which claims Rishi Sunak does not think child sex abusers should go to prison.

Shadow culture secretary Lucy Powell said the post was part of “political campaigning” but admitted: “It won’t be to everybody’s taste.”

Asked whether she was “comfortable with pointing the finger at Rishi Sunak”, Ms Powell told Sky News: “I’m comfortable with taking a sort of standardised graphic, that the prime minister used himself many, many times in recent months and years, to highlight how one of his own policies isn’t working.”

She added: “It’s political campaigning. I’m comfortable to be on your programme this morning defending what we’re talking about, which is some really serious issues around the criminal justice system and how this country is just not dealing with that.”

Labour has been accused of “gutter politics” and criticised by its own MPs after posting a message on its official Twitter account vowing to “lock up dangerous criminals”.

The tweet pointed to data from the Ministry of Justice showing that 4,500 adults convicted of sex acts on children avoided a prison sentence since the Conservatives came to power in 2010.

It said: “Do you think adults convicted of sexually assaulting children should go to prison? Rishi Sunak doesn’t.”

The language has been widely criticised, with many drawing comparisons to Boris Johnson’s false claim last year that Labour leader Sir Keir Starmer failed to prosecute Jimmy Savile when he was director of public prosecutions.

Veteran Labour MP John McDonnell said: “This is not the sort of politics a Labour Party, confident of its own values and preparing to govern, should be engaged in.

“I say to the people who have taken the decision to publish this ad, please withdraw it. We, the Labour Party, are better than this.”

Conservative peer Baroness Sayeeda Warsi also condemned Labour’s tweet while hitting out at her own party for triggering an “appalling fight into the gutter”.

She said: “Dog whistle met by dog whistle.

“Disgraceful comments by Braverman over the weekend has triggered an appalling fight into the gutter.

“At what point are we going to talk about the victims? Where is the protection for the half million kids sexually exploited in our country every yr.”

Last week, Home Secretary Suella Braverman claimed Labour-run areas failed to stop child grooming gangs over fears they would be called “racist”.

The row has renewed calls for tighter laws around political campaigning, as both main parties seek to sell themselves as strong on law and order ahead of the local elections.

Row shows need for law ‘requiring honesty in politics’

Compassion in Politics, a campaign group working to “clean up” public debate in Britain, called on Sir Keir to withdraw the ad and apologise.

“This kind of political discourse poisons the water that we all must drink from. It drives up hate and drags down standards,” co-director Jennifer Nadel told Sky News.

“Sir Keir Starmer has rightly identified that the public want to see politicians act with respect, dignity, and decency. He can start by pulling this ad from circulation and issuing an immediate apology.”

Compassion in Politics has worked with lawyers to create a new bill which would make it a criminal offence for politicians to lie to the public, punishable by a fine or jail.

The bill is being sponsored by Plaid Cymru MP Liz Saville Roberts while over 200,000 people have signed a petition backing it.

Ms Nadel said incidents like this show why “going forwards, we need to look at the levers we can pull to really clean up our politics”.

“We would introduce a law to require that political communications are based on honesty and truth and to ensure that breaches of the founding principles of our democracy – accountability, respect, and toleration – can be investigated and acted upon,” she said.

“If we’re to solve the problems we face as a nation and build a country that is inclusive, caring, and prosperous we have to start working together to achieve that goal.”

A Labour spokesman declined to comment on the backlash to the tweet.

He said: “The Conservatives have left dangerous convicted criminals free to roam the streets.

“Labour is the party of law and order, and we will implement tougher sentences for dangerous criminals.”