Lennox, a UN Aids Ambassador, spoke in the final session of the International Parliamentary Conference on the Millennium Development Goals (MDGs) hosted by the Commonwealth Parliamentary Association (UK Branch).
Speaking at a session chaired by Commons Speaker Rt Hon John Bercow MP, the singer urged parliamentarians, both in Britain and across the Commonwealth, to "influence and enact change" in the global fight to combat HIV/Aids.
Coinciding with World Aids Day, Lennox's speech focused on how politicians around the world needed to tackle the Aids pandemic – one of the eight MDGs.
She told delegates: "You are the people the public look towards to influence change. It is for you as politicians to face the never-ending issue of tackling these issues."
And Lennox quoted Nelson Mandela, the former South African president, whom she said had first inspired her to campaign for greater awareness of HIV/Aids.
"Mandela said 'it is in your hands', and it truly is in your hands," Lennox told conference delegates.
Also speaking at the session was Rt Hon Lord Malloch-Brown KCMG PC, former deputy Secretary-General of the UN.
In his role as administrator of the United Nations Development Programme, Malloch-Brown had been responsible for devising the Millennium Development Goals.
Describing how his main objective, whilst at the UN, had been to utilise democracy as "a means to an end – namely accountable development for the poor", he urged the political class to continue to pursue the Goals as a matter of course.
"The MDGs were written for you – politicians," he said. "Parliamentarians must pick up the baton of the MDGs. This is the biggest challenge of our time."
Davies Banda, senior lecturer in sport policy and development at York St John University, also spoke at the session. He emphasised the importance of sport as a tool for international development at both a social and economic level.
"Sport can be used as an effective vehicle for social mobilisation and education," Banda noted. "Sport has the potential to connect people and communities from diverse backgrounds."
Providing the closing statements at the conference, attended by over 100 participants from both Commonwealth and non-Commonwealth nations, the Speaker of the House of Commons, Rt Hon John Bercow, highlighted his previous work on the international development select committee.
Continuing Banda's theme of the importance of sport to development, Bercow told delegates of his experiences visiting Darfur on a parliamentary delegation, where he and colleagues had handed out footballs to be used by children who had been playing the sport with a makeshift ball made of up of condoms and string.
The United Nations Millennium Development Goals have a target date to meet of 2015. They are eradicating extreme poverty and hunger, achieving universal primary education, promoting gender equality and empowering women, improving maternal health, combating HIV/Aids, malaria and other diseases, ensuring environmental sustainability, developing a global partnership for development.
The International Parliamentary Conference on the Millennium Development Goals 'Reaching for 2015: Governance, Accountability and the Role of the Parliamentarian' took place from 28 November – 2 December 2011.