In autumn 1998, I was 18 years old and a new student of management at Brunel University in Uxbridge, west London. I was becoming increasingly interested in my Islamic faith - and, like many people of that age, in challenging some of the injustices of the world. The Hizb ut-Tahrir stall at the freshers' fair offered me a way of doing just that.

Hizb ut-Tahrir ("The Liberation Party") aims to replace all existing governments with a global khilafah, or caliphate, subject to Islamic law and ruled by an elected male caliph. Founded in 1953 by Taqiuddin al-Nabhani, an Islamic scholar from Jerusalem, it now has about one million members spread through 40 countries, in some of which it has been banned. The party is secretive and hierarchical, with a network of national branches, each headed by an emir, or leader, who in turn is subject to an overall leader based in Palestine. Female members have their own parallel structure subject to the same leadership.

The party's arguments were persuasive. It offered a single, simple solution to all the political, social and economic problems of the world, from a religious perspective. Why should religion be left in the mosque? it asked. It should guide every aspect of our lives, particularly politics.

Hizb ut-Tahrir emphasised that it was not encouraging jihad - that it was a political and intellectual movement. Its rhe toric, however, was antagonistic, and often controversial. Its pamphlets argued that the west was out to destroy Islam, or that Jews must be removed from Israel for peace to come to the Middle East. It aimed to tap into a pre-existing anger felt by many young Muslims. It attracted a lot of hostility among the community - many of my friends disagreed with its aims and aggressive tactics. But to me, its ideas sounded new, fresh and exciting.

Cult-like structure

I became affiliated with the group, distributed its literature and, over the next few years, worked my way towards becoming a full member. In the strict hierarchy of the organisation, this was not a simple task. The new recruits aspired to become daris, or "students", who in turn aimed to take an oath of loyalty to Hizb ut-Tahrir and become full members. All the women were expected to use any social contact they had to recruit new members - mother-and-baby groups, student unions, even a chat with the neighbours. After proving their commitment to the party, they were assessed by a committee and allowed to attend the weekly "culturing circle". At 20, I joined them.

This circle was also known as a halaqa - a word other Muslims use for small groups that meet to study Islam or recite the Quran. But in the Hizb ut-Tahrir halaqa, we spent two hours listening to readings from books by the party founder, al-Nabhani. His book Nidham al-Islam ("the system of Islam") very briefly sketched the practicalities of setting up a new world order. But we did not even discuss the party's goal on that level. Everyone simply accepted that, through the hard work of party members, each country would embrace Hizb ut-Tahrir concepts and demand that its government make a peaceful transition to the khilafah, and then "we would know what to do when we got there". Originally, the holes in al-Nabhani's thinking did not trouble me. Later, however, I realised that the halaqa and the party philosophy made his writings synonymous with the Quran. In Hizb ut-Tahrir, religion and politics were truly confused.

But the cult-like structure of the organisation made this difficult to see. When I was 21, I became a full member - a prestigious position - and shortly afterwards was put in charge of the women's group's activities in west London. Suddenly, I was privy to information kept from non-members, such as the location of meetings and the details of organisational policy.

For young people - the vast majority of the members and the leadership were aged between 17 and 25 - the sense of power and community was intoxicating. We even had a very specific dress code that was chosen by the emir of HT. He had made it mandatory for all members to wear the jilbab (a loose dress), khimar (headscarf) and socks. Many Muslim women wear the jilbab and scarf, but for some reason I could always identify a fellow HT member; perhaps it was from their uniform-like style.

For a few years, I worked for the party in the Muslim community. I organised events, lectures and bazaars, renting venues and arranging marketing with the budget I was assigned from party donations. I was sometimes frustrated with these events - they were an inefficient way of recruiting members and rarely seemed to get the party message across. But, for a while, I put the doubts out of my mind.

In 2006, however, my feelings began to change. I noticed that whenever I had concerns, I was told to raise them through "the structure", but the answers to my questions and challenges were not satisfactory. The senior members seemed to be on autopilot, speaking only in party jargon, unable to participate in debate or look at the other side of an argument. It was certainly frowned upon for anyone to air their views freely or to make challenging statements. I began to question the leaders' claim that it was a God-given obligation for every Muslim to work with the group. How could this possibly be the case when these people were so far removed from society and normal life? I was fast losing confidence. But, surrounded by other members, I felt guilty about such sentiments. I stuck with it for a year, selling tickets for the same old talks and events, attending pointless meetings, and boring myself and others with "Hizbi" banter.

Finally, I was reported to the leadership as a "breakaway" member - party code for anyone who questions the party's principles. The women's emir travelled from east London to my home, bringing her small children with her. She could not answer my questions about the party any better than the local leadership.

"If we're supposed to be promoting peace, then let's do so," I told her. She replied that I had strayed from the party's principles and that I could not think in those terms. Eventually, I had to tell her that I was resigning my membership. Since then I have had almost no contact with Hizb ut-Tahrir.

After leaving, I realised that my aspirations had changed. I wanted to live as a normal member of society, and practise Islam as best I could in that context. Suddenly, I became aware of a chorus of moderate voices who supported me. I took off the party-approved jilbab, though I still wear modest dress. It was an enormous relief.

I realised that Hizb ut-Tahrir has devised a set of political ideas and goals which are in fact separate from Islam. Its tactic of convincing young people that its political goals are synonymous with Islam is its most dangerous and deceptive trick. In reality, its aims come from one man's socialist ideals, mixed with his own interpretation of Islamic scripture. So it is not "sacrifice in the way of Allah" to aid the overthrow of a government or to work with such a group.

It is my desire to witness security, safety and peace in the Muslim world. But will this come about through the forceful removal of all current Muslim governments? This is a point that Hizb ut-Tahrir leaders refuse to discuss with the naive recruits or to think about for themselves. The leaders claim to believe that the blood of a Muslim is sacred, but would be happy to spill it themselves if anyone were to oppose their khi lafah regime.

A party text by Abdul Qadeem Zallum, the second leader of HT, states that if necessary millions of Muslims and non-Muslims will be killed. How would this fact make the party different from the tyrannical rulers it continuously curses and defames?

I no longer agree with the politics and principles of Hizb ut-Tahrir, and I urge other members to reconsider their affiliation with this potentially dangerous group. They should seek a wider knowledge of Islam and open themselves to more tolerant opinions.

Umm Mustafa is a pseudonym