Pakistan is failing to live up to one of the tenets of Islam which guarantees rights to all women, according to Sayeeda Warsi, the Conservative party co-chairman and minister without portfolio, who is the first Muslim to sit as a full member of the cabinet.

In a sign of Britain's impatience with Pakistan, Lady Warsi said the world's first Islamic republic is denying rights granted 1,400 years ago in the Qur'an.

As she prepares to become the first British minister to address the Organisation of the Islamic Conference (OIC) next week, Warsi said in a Guardian interview that, in a "nutshell", Pakistan is not living up to the ideals of its founding father, Muhammad Ali Jinnah.

Warsi says she is able to deliver a tough message to Pakistan because she is unencumbered by "colonial baggage". She said she had raised the issue of women's rights last July in Rawalpindi, in a speech in Urdu at the Fatima Jinnah University, named after the younger sister of the founder of Pakistan. "Why is it that today you're being denied the rights that your faith gave to you 1,400 years ago?" Warsi asked, recalling her central message to her female audience.

Warsi, 40, whose father arrived in Britain from Pakistan in 1960, will address a meeting of OIC foreign ministers next week in Astana, the capital of Kazakhstan.

Campaigners have warned about the treatment of women in north-west Pakistan where justice is administered in some areas by tribes through the jirga rather than by the state. Women usually suffer harsher treatment when couples are sentenced to be stoned to death for adultery. Samar Minallah, a women's rights activist, warned last year: "In so many past cases, the woman was killed later on, or married off for a bride price. They just can't let her be, there has to be revenge."

Warsi said she had also raised concerns about the treatment of minorities in Pakistan. Shahbaz Bhatti, Pakistan's only Christian minister, was shot dead in March after he called for the reform of blasphemy laws that impose the death sentence for insulting Islam.

Warsi said: "I said to them ... let me talk to you about the rights of minorities, the protection of women and the concept of meritocracy. I gave real examples of how Islam embodies all of those values, and the question I put was: my country wasn't formed in the name of Islam, but yours was; so why does my country embody the values of the faith that your country was formed on the basis of?"

Warsi said her heritage enabled her to speak out. "This was not the west arriving with an ideological perspective of women's rights about to impose them on a nation. I understand this culture, I deeply understand the faith and the culture that is part of this nation ... But what I don't see is you in many ways having the very values upon which the nation was formed, the vision of the founder of Pakistan."

Since appointment to the cabinet Warsi has visited Muslim countries, including Kuwait and Pakistan on four occasions. She played an important role in smoothing relations with Pakistan after David Cameron caused great offence last July when he said in India that elements of the Pakistan state were guilty of exporting terrorism.

Warsi, who recalls how she wore a pink shalwar kameez on the day she was appointed, believes her presence in cabinet challenges "the kind of lazy prejudice" that says in the Muslim world and in Britain that somebody from her background cannot be a government minister.

"I don't believe in this clash of civilisations, where there is the west and the Muslim world," she said. "I mean, if I did, where would I fit in?"

Warsi travels to Astana after she met Ekmeleddin Ihsanoglu, secretary general of the OIC, during a visit to its secretariat in Jeddah last year while she was in Saudi Arabia for the hajj. This led to the appointment of Britain's first special representative to the 57-strong group. "This is an organisation which is good to engage with and have much deeper engagement with but clearly that relationship didn't appear to be there twelve months ago," Warsi said.

Ihsanoglu recently raised concerns about Islamophobia with Warsi, who caused some controversy in January by saying this had "crossed the threshold of middle-class respectability". They had both agreed that Britain has a better track record than other European countries.