Mr Abu Rahmah was convicted by a military court on Monday on charges of "incitement" and "organising and participating in an illegal demonstration." He was cleared of stone throwing and possession of arms.

The 39-year old activist, in jall having been detained in December and now awaiting sentence, is a protest leader in the West Bank village of Bil'in. He faces a maximum sentence of 10 years. The protests are generally peaceful but often see stone-throwing by young protesters.

"The EU considers Abdallah Abu Rahmah to be a human rights defender committed to non-violent protest against the route of the Israeli separation barrier ... The EU considers the route of the barrier where it is built on Palestinian land to be illegal," said Ms Ashton is a statement. The EU has attended all the court hearings over the past eight months.

Her words came a week before the start of the first direct talks between Israel and the Palestinians for more than 18 months.

"The high representative is deeply concerned that the possible imprisonment of Mr Abu Rahmah is intended to prevent him and other Palestinians from exercising their legitimate right to protest against the existence of the separation barriers in a non-violent manner," the statement continued.

UK daily The Guardian reports a spokesperson for the Israeli foreign ministry as saying that Ms Ashton had no right to make such comments.

"It is very unusual for a foreign dignitary to express views on the justice system of another country. If [Ashton] has found a flaw in the system, she should say so. Otherwise it's unclear why she should interfere in the proceedings. The fact that she has expressed a view and has disregarded the evidence is highly improper," said spokesperson Yigal Palmor.

The Popular Struggle Co-Ordination Committee called the charge "absurd," reports the UK's Independent, adding it showed how far the military would go "to silence and smear unarmed dissent."

The Committee also said that charge of organising demonstrations under Israeli military law had not been used since the first intifada starting in 1987.

Ms Ashton's intervention comes in the context of Quartet (the EU, Russia, the Un and the US) efforts to rebuild trust between Israel and Palestine in a fresh round of peace talks due to start on 2 September.