Last updated on .From the section Athletics

Maryam Yusuf Jamal, Asli Cakir Alptekin and Gamze Bulut pose with their Olympic medals - Jamal is the only one of the three never to have failed a drugs test

Former Olympic 1500m champion Asli Cakir Alptekin has been banned for life after a third doping offence.

In 2015, the 32-year-old was stripped of her 2012 Olympic and European titles and suspended for eight years by the Turkish Athletics Federation.

She returned this year after the ban was halved and its start date backdated to 2013, but has since reoffended.

"We are never, ever going to allow doping," said Turkish Athletics Federation chief Fatih Cintimar.

Six of the first nine finishers in the women's 1500m final at the 2012 Olympics have been given drugs bans, leading some to refer to it as the "dirtiest race in history". external-link

Straight after the race, Britain's Lisa Dobriskey, who finished 10th, told BBC Radio 5 live: "I don't believe I'm competing on a level playing field."

Cakir Alptekin previously served a two-year ban following a positive test at the 2004 World Junior Championships.

She finished 11th in the European Champion Clubs Cup Cross Country event in Portugal in February, helping Uskudar Belediyespor win the title.

The nature of her latest offence has not been made public.

'The dirtiest race in history' - how they finished

1st Asli Cakir Alptekin, Turkey - four minutes 10.23 seconds

Had served a two-year ban prior to winning gold, and only finished a four-year suspension earlier this year. Now banned for life.

2nd Gamze Bulut, Turkey - 4:10.40

Set a personal best of 4:01.18 in the semi-final. Prior to that year, her personal best was 4:18.23. Serving a four-year suspension until May 2020.

3rd Maryam Yusuf Jamal, Bahrain - 4:10.74

Has never failed a drugs test. Prior to winning Olympic bronze in 2012, she was the world champion in 2007 and 2009.

4th Tatyana Tomashova, Russia - 4:10.90

Prior to the 2012 Games, the 2003 and 2005 world champion had served a ban of more than two years for manipulating samples before a doping test.

5th Abeba Aregawi, Ethiopia - 4:11.03

Former world champion, who has competed for Sweden since 2012, was provisionally suspended last year after she tested positive for meldonium, though that was later lifted.

6th Shannon Rowbury, United States - 4:11.26

Has never failed a drugs test. Her most impressive performance to date came in July 2015, when she broke the American record that had stood for nearly 32 years.

7th Natallia Kareiva, Belarus - 4:11.58

Was banned in 2014 for a biological passport abnormality and her Olympic result was voided.

8th Lucia Klocova, Slovakia - 4:12.64

Has never failed a drugs test. Competing in her third Olympics, she had run the 800m in the previous two.

9th Ekaterina Kostetskaya, Russia - 4:12.90

Was given a two-year ban in 2014 for violating an IAAF rule against "use/attempted use of a prohibited substance/method" at the 2011 World Championships.

10th Lisa Dobriskey, Great Britain - 4:13.02

Has never failed a drugs test. Lost out on a medal at the Beijing Olympics when she was pipped for bronze by Ukrainian Nataliya Tobias, who later tested positive for testosterone.

11th Laura Weightman, Great Britain - 4:15.60

Has never failed a drugs test. Weightman, who reached the 2012 and 2016 Olympic 1500m finals, says she believes there had been "huge steps forward" in the past four years.

12th Hellen Onsando Obiri, Kenya - 4:16.57

Has never failed a drugs test. Won 5,000m gold at this year's World Championships in London.