Anti-Austerity Alliance deputy Paul Murphy insisted President Higgins was a legitimate focus for campaigners to demonstrate against, as he had signed the water charge bill into law without referring it for review.

However, Mr Murphy also urged protesters to stop calling the President a “midget” because such language is “ableist” — meaning it is offensive to people of restricted growth.

Video footage of demonstrators chasing after Mr Higgins’ car and shouting at the head of state has sparked a storm of reaction, as the office of the President has traditionally been viewed as above party politics and policy issues.

The video, taken as the President left a school in Dublin last Friday and posted on YouTube by water charge protesters, reveals unprecedented scenes of protesters directing expletives at the President and shouting personal insults such as “you little midget parasite” and “you little sell-out”, and branding him a “traitor”.

Dublin South West TD Mr Murphy, who had a prominent role in a protest in November which saw Tánaiste Joan Burton hit by a water balloon and trapped in her car for more than two hours, insisted the President should not be allowed to escape protest.

“I defend their right to protest, including against the President because people are angry that he signed the bill,” Mr Murphy told the Irish Examiner.

Mr Murphy has consistently refused to apologise for his role in the demonstration which saw the Tánaiste trapped in her car — an incident Taoiseach Enda Kenny condemned for the homophobic and sexist abuse of gardaí — but nonetheless was critical of some of the language used in the abuse of the President.

“I would not agree with personalised comments and midget comments, which are ableist. It’s not a nice word for people to be using,” he said.

“I don’t think there is a lot of point targeting him tactically, but he did sign a piece of legislation which means people have the right to protest about that.”

By President Higgins signing water legislation into law Paul Murphy can now challenge it in a court. Why won't he? #RTElatedebate — Joe Ryan Wex (@JoeRyanWx) January 27, 2015

Gardaí said the incident was being investigated and Mr Higgins’ protection was being looked at.

“The incident is under investigation and security surrounding the President is constantly under review,” said a Garda spokesperson.

Labour chief whip Emmet Stagg said: “This type of behaviour is outrageous. They should back off. the office of the president is above party politics.”

A spokesperson for Áras an Úachtaran refused to comment on the incident, or any possible increase in the level of security surrounding the President.

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