The UK government is being urged to increase the amount of money it spends fighting Aids in Africa.
The trade union Unison, the National Union of Students and Action for Southern Africa say the UK should triple the amount it spends.
The groups will urge MPs to join their campaign at a meeting in the House of Commons later on Tuesday.
They are trying to influence the government's spending review, which is due to be announced in July.
The review, which is being carried out by Chancellor Gordon Brown, will determine government spending priorities for the period 2005 to 2008.
The Department for International Development submitted its bid for increased funding on Tuesday.
Campaigners want the government to dramatically increase the amount of money it contributes to the Global Fund to fight Aids, Tuberculosis and Malaria.
The fund is playing a key role in helping many people with HIV to get the anti-retroviral drugs they need to fight the disease.
Campaigners say the UK has only contributed one third of what it should to the fund.
"Money should not be the barrier in the fight against Aids," said Aditi Sharma, Action for Southern Africa's campaigns director.
"We are asking MPs to support our campaign to end the scourge of Aids that is killing 6,500 Africans every day.
"We need a concerted effort from our parliamentarians to ensure that our government starts writing cheques to back their promises to Africa."
Mandy Telford, president of the NUS, said: "The UK government needs to lead by example and increase spending in the fight against HIV/Aids.
"Funding the Global Fund is the only way that HIV/Aids can be tackled on an international level and a committed coalition of nations can be inspired by Britain taking bold steps in the right direction.
"Money must also be found for domestic issues. Rising STI infection rates will only be challenged by the provision of quality and accessible sexual health advice and education for everyone."
Dave Prentis, general secretary of Unison, also called for extra money.
"The Aids in Africa statistics are appalling. Words of sympathy are not enough - our government must act urgently to help those caught up in this ever-increasing tragedy.
"Our MPs must press the Treasury in the strongest terms how much that cash help is desperately needed."