Surjit Athwal, 27, originally from Coventry, was killed in India in 1998. <br />Her mother-in-law Bachan Athwal and husband Sukhdave Athwal, of Hayes, west London, were jailed at the Old Bailey in 2007 for arranging her murder. <br />Jagdeesh Singh said those paid to murder his sister remain free in India and called for a new investigation. <br />Surjit Athwal was killed during a trip to the northern Indian state of Punjab in 1998. Her body was never found. <br />Mr Singh has written a letter to David Cameron to mark what would have been her 42nd birthday. <br />"He can press the Indian Prime Minister for a full scale investigation into this case," he said. <br />"Although, there was an investigation conducted by the Punjab police in 2000, there were no convictions for men who killed my sister."
