The campaign organisation Fathers4Justice (F4J) has said it believes one of its members tried to write 'help' on a portrait of the Queen in Westminster Abbey.
Campaign Director Jolly Stanesby said the member, who is allegedly a father from Doncaster, had "felt he had nothing to lose by appealing directly to the Queen for help".
– Fathers4Justice statement
We understand that a desperate father belonging to Fathers4Justice has attempted to write the word 'help' on a portrait of the Queen in Westminster Abbey at lunchtime.
The father...was trying to petition the Queen for help before Father's Day on Sunday.
Up to 4 million children will be without a father this Father's Day.
[He] has lost all contact with his children and felt he had nothing to lose by appealing directly to the Queen for help by spraying his plea onto her portrait."
This photograph purports to show the portrait of the Queen after it was defaced at Westminster Abbey.
It appeared on the Facebook page of the campaign group Fathers4Justice, which has claimed that some of its members took responsibility for the act.
ITV News cannot independently confirm the veracity of this image.
Campaign group Fathers4Justice said one of its members was responsible for damage to a portrait of the Queen, in an apparent "Father's Day protest".
A spokesman said it was not an official protest.
Painted by Australian-born Mr Heimans, the piece measures 9ft by 11ft and depicts the monarch in the Sacrarium of Westminster Abbey, also known as the Coronation Theatre.
The painting is entitled The Coronation Theatre, Westminster Abbey: A Portrait of Her Majesty Queen Elizabeth II.
It was shown publicly for the first time in September by the Australian governor-general Quentin Bryce at the National Portrait Gallery in Canberra.
It was moved to London and put on display in Westminster Abbey last month.
Officers were called to Westminster Abbey around 12.30pm today after security guards detained a 41-year-old man.
He was arrested on suspicion of criminal damage and taken to a central London police station where he is in custody, a Metropolitan Police spokesman said.
The portrait, a Ralph Heimans' oil on canvas designed to commemorate the Queen's Diamond Jubilee, had been on display in the Chapter House for a few weeks before it was vandalised with paint.
A 41-year-old man was arrested today on suspicion of criminal damage after a portrait of the Queen was defaced in Westminster Abbey, Scotland Yard said.
A portrait of the Queen at Westminster Abbey has been removed from public view after it was defaced, an Abbey spokesman confirmed.
The painting, by artist Ralph Heimans, had been on display in the Chapter House for a few weeks before it was vandalised with paint.
It was unveiled in London last year for the Queen's Diamond Jubilee celebrations.
An Abbey spokesman said: "In an incident at lunchtime today, a visitor to the Abbey sprayed paint on the Ralph Heimans portrait of the Queen presently on display in the Chapter House.
"Until work can be done to remedy the damage it will, very regrettably, not be possible to have the painting on public view."
A portrait of the Queen in Westminster Abbey has been defaced with paint, a spokesman for the Abbey said today.