British cyclist Lizzie Armitstead has insisted that she will 'hold her head high' at the Rio Olympics after receiving "incredibly painful" criticism for missing three drug tests.

The 27-year-old was suspended by the UK Anti-Doping Agency for the violation, but the Court of Arbitration for Sport struck one of the failures from her record following an appeal by the cyclist.

It was unanimously decided that the first test at a World Cup event in Sweden in August 2015 was missed because the official could not get hold of her at a hotel because she was sleeping with her phone on silent.

Three test failures within 12 months can result in a four-year ban, but due to CAS's ruling, Armitstead is free to compete in this Sunday's road race at the Olympics in Brazil.

After receiving criticism, Armitstead tweeted a two-page document explaining the circumstances surrounding the missed tests, revealing that the second was an administrative error on her part on October 5 and the third, which was due to be held on June 9 this year, was missed due to "an emergency family situation".

The cyclist, who won silver at the London 2012 Olympics, insisted that she has never tested positive for a banned substance.

She added: "In the days following the revelations in the press, my family and I have been the victim of some incredibly painful comments. I as people to take a moment to put themselves in my shoes. I am an athlete trying to do my best, I am a clean athlete.

"I love sport and the values it represents. It hurts me to consider anybody questioning my performances. Integrity is something I strive for in every part of my life. I will hold my head high in Rio and do my best for Great Britain.

"I am sorry for causing anyone to lose faith in sport. I am an example of what hard work and dedication can achieve. I hate dopers and what they have done to sport."

Armitstead won road-race gold in the World Championships last year.