MPs have expressed concern about the "tone and timing" of Afghan president Hamid Karzai's comments about the UK.
The Afghan president has criticised British military operations in the country
The Commons International Development Committee said such criticism could undermine British public support for long-term commitment to Afghanistan.
It said it was "disappointed" by Mr Karzai's comments last month that British military operations had made the situation in Afghanistan worse.
A government spokesman said the UK fully supported the Afghan government.
It was committed to helping bring peace and stability to the country, he said.
In a report, the committee said criticisms of UK efforts "seem to be becoming more frequent".
Its Lib Dem chairman Malcolm Bruce said: "We are concerned about the recent deterioration in political relations between the government of Afghanistan and the UK.
"We recognise that the civilian and military effort is entirely dependent on the goodwill of the government and people of Afghanistan.
"But there is a risk that the tone and timing of recent comments by the government of Afghanistan which are critical of the UK could undermine British public support for the UK's long-term commitment to Afghanistan."
The committee said it would take at least a generation to develop Afghanistan, and abandoning it could have repercussions for global security.
It expressed disappointment that agreement had not been reached on one high-level figure to oversee UN, EU and Nato aid programmes - Lord Ashdown pulled out of the role in January, saying he did not have the backing of the Afghan government.
The report said: "We hope that the government of Afghanistan can recognise the long-term benefits for them of the UN appointing a strong representative to improve co-ordination."
It also said corruption and bribery were "rife" in the training of the Afghan national police force, and expressed concern about reports that state officials were involved in the opium trade.
But it criticised US aid efforts for not directing money through the Afghan government, saying it was "preventing the Afghans having ownership of the reconstruction of their country".
About 80% of UK government assistance goes through government channels.
The report said while the position for women had improved, they were still the victims of widespread violence in Afghanistan due to "'cultural' differences and local traditions". Reform of the justice sector should be a priority, it said.
Mr Bruce said Britain had to be "realistic about what can be achieved in the short term" in Afghanistan.
But he said it was vital that the international community stay committed to the reconstruction effort, "since the insurgency will not be defeated without tangible improvements in people's lives".
A spokesman for the Department for International Development said the UK had a long-term commitment to Afghanistan.
"We fully support the Afghan government and continue to work with it, President Karzai and the international community in the interests of the Afghan people," he said.
"The prime minister's statement to the House of Commons in December confirmed the UK's commitment to building Afghan-led security, governance, and development."