King Hamad bin Isa al-Khalifa reassured David Cameron yesterday that reform in Bahrain is under way after a devastating report confirmed the mass use of torture against pro-democracy protesters earlier this year. Mr Cameron will be glad to hear this since the UK and US have been embarrassed at having to explain why they have been outraged by human rights abuses in Libya and Syria, but far less critical when it comes to their ally in Bahrain.

But the opposition, drawn from the Shia who make up 70 per cent of the island's Arab population, say the focus on redressing grievances, stemming from the repression of peaceful protests, is masking a long-term policy of depriving the Shia of all decision-making jobs. "Every day Bahrainis of the Shia faith are being dismissed from decision-making positions," says Mansoor al-Jamri, a newspaper editor and Shia leader. "The emphasis on stopping torture is camouflage for establishing a confessional-based apartheid system."

Mr Jamri says that at the time the British withdrew from Bahrain in 1971, important jobs were split 50:50 between Shia and Sunni. Although the majority of citizens, the Shia have since seen their proportion of top jobs at the ministerial and senior civil servant level drop to 17 per cent by the year 2000 and to less than 5 per cent today, he says. All real power is in the hands of the Sunni al-Khalifa dynasty which is backed by Saudi Arabia.

Shia leaders say that, while they had always been excluded from top jobs in security, they are now being dismissed from decision-making positions in health, education and agriculture ministries. They fear this is a long-term policy that is unconnected to more than 2,000 Shia sacked from government service after the authorities moved to crush protests on 15 March, many of whom have been re-employed.

Bahrain's government yesterday flatly denied it is trying to establish a sectarian system in which the Shia would be the underclass. An official spokesman said: "It is simply not true that people are being dismissed on sectarian grounds from their jobs, and the government of Bahrain would abhor and condemn such a practice."

The perception by the Shia in Bahrain that, in the long term, the government wants to alter the balance against them and in favour of the Sunni is an explosive issue. Shia leaders warn that a sense that they are being denied the chance of promotion to senior positions will inevitably provoke a crisis. The Arab Awakening in Bahrain started on 14 February with huge rallies taking place in Pearl Square. The al-Khalifas evidently interpreted the movement as an attempt to overthrow them and called in a Saudi-led 1,500-strong military force on 14 March. The following day, the government launched a ferocious campaign of arrests, imprisonment, beatings and torture.

The extent and severity of the brutality was detailed last month in a report commissioned by King Hamad and headed by the distinguished Egyptian-American lawyer Cherif Bassiouni. He received 559 claims of torture, all but nine of them from Shia, and forensic studies of victims showed a diverse range of torture techniques. Committees have been appointed to implement the findings of the report.

The UK and US have a further undeclared motive in talking to King Hamad and Crown Prince Salman bin Hamad. This is to buttress their authority, which has been severely eroded within the royal family this year by harder-line members led by the Prime Minister, Khalifa bin Salman.