The rate of beheadings and Islamist-inspired stabbings has risen 11-fold in the last five years according to a major new report. Terror attacks in the UK also tripled during this period.

The 1000-page report by the Henry Jackson Society examines all terror convictions and suicide attacks inspired by Islamism in the UK between 1998 and 2015. It warns “Islamism-inspired terrorism remains the principal terrorism threat”.

The report recorded 269 convictions during the period, involving 253 individuals. 72 per cent of those who committed Islamism-related offences (IROs) were British nationals. 16 per cent were converts to Islam.

The report states: “The 269 Islamism-related offences (IROs) comprise 135 distinct terrorism cases.

“The rate of offending increased in the five-year period between 2011 and 2015 compared to the 13-year period between 1998 and 2010.

“IROs doubled in five years (increasing from an average of 12 to 23 per year) while distinct terrorism cases almost tripled (from five per year to 14 per year).”

The most common place of arrest for IROs were ethnically diverse areas, with London accounting for 42 per cent of the total, and Birmingham 14 per cent.

The 2011 census showed just 45 per cent of London’s population belonging to the white British category, whilst a 2013 report found that fewer than a third of schoolchildren in Birmingham were white.

The study found “little correlation between involvement in terrorism and educational achievement and employment status”, with a quarter of IROs having been committed by individuals who had some form of higher education.

According to the report, 22 per cent of the people convicted had attended terrorist training camps while 44 per cent had direct links to a proscribed terror organisation, the most common of which were the UK-based al-Muhajiroun, al-Qaeda (10 per cent overall) and Islamic State.

Prevent, the government’s major deradicalisation program, has been attacked by activists, unions and other bodies for being “racist”, and discriminatory towards Muslims.

Conservative MP Lucy Allan last month reported that increasing pressure on teachers to refer children to the Prevent Strategy for reasons other than radical Islam has led to schools considering whether attendance at a fathers’ rights march or a protest against badger culls could qualify a pupil for referral.

And in January, a 15-year-old schoolboy who thought “Muslim women shouldn’t be allowed to wear the niqab”, was identified as a potential terrorist and put through the government’s strictest de-radicalisation programme.