The Prime Minister has said Russia is backing the "butcher" Bashar Assad through air strikes which are not solely targeted at Islamic State militants in Syria.
Mr Cameron's remarks echo the words defence secretary Micheal Fallon used in a newspaper interview, where he said military intervention by Putin in Syria was to help prop-up the Assad's brutal regime.
Russian aircraft have attacked the so-called Islamic State group in central and northern Syria, a Syrian military official has said.
The "concentrated and precise" airstrikes destroyed a command centre in the central town of Latamneh and targeted positions in the north-western areas of Jisr al-Shughour and Maaret al-Numan, the official told state TV.
However, in an interview with The Sun newspaper, British defence secretary Michael Fallon warned that only "one in 20" Russian strikes so far were on targets that were linked to the jihadists and that Putin was using his military forces to prop up Syrian president Bashar Assad's brutal regime.
Civilians are being killed by Russian airstrikes and military intervention in Syria, Defence Secretary Micheal Fallon has said.
Mr Fallon said the the "vast majority" of strikes since Vladmir Putin authorised raids in the war-torn country had not been against Islamic State jihadists but were instead "killing civilians" and the Free Syrian forces rebelling against Bashar Assad's brutal regime.
He said that Russia's military intervention in Syria was propping up Assad rather than tackling the treat from the so-called Islamic State.
Fallon acknowledged the Russian involvement had "complicated" the situation but indicated he still believed that Britain should extend its own bombing campaign to target IS in Syria.
In an interview with The Sun he said initial Ministry of Defence intelligence suggested only one in 20 Russian air strikes so far were on targets to damage IS.
He said: "We're analysing where the strikes are going every morning. The vast majority are not against IS at all.
"Our evidence indicates they are dropping unguided munitions in civilian areas, killing civilians, and they are dropping them against the Free Syrian forces fighting Assad.
"He's shoring up Assad and perpetuating the suffering."
The Syrian conflict will not become a "proxy war" between the United States and Russia, President Obama has said.
Mr Obama said he wanted Russia to be successful and help deal with global problems, but its approach to Syria was not a "smart strategic move".
"This is not a contest between the United States and Russia," the US President told a press conference on Friday.
"We're not going to make Syria into a proxy war between the United States and Russia. That would be bad strategy on our part.
"This is not some superpower chessboard contest."
Russia's approach to the conflict in Syria is a "recipe for disaster", Barack Obama has warned.
The US President said Russia and Iran were to blame for President Bashar al-Assad remaining in power.
President Obama said air strikes against the moderate Syrian opposition would be counter-productive and strength Islamic State.
Discussing Russian President Vladimir Putin's approach to the situation, President Obama said: "He doesn't distinguish between ISIL and a moderate opposition that wants to see Assad go.
"From their perspective they're all terrorists, and that's a recipe for disaster and it's one that I reject.
"What Russia is doing now is not particularly different from what they have been doing in the past, they're just more overt about it. They've been propping up a regime that is rejected by an overwhelming majority of the Syrian population."
Russian fighters attacked Syria for a third day, bombing Islamic State targets as President Putin met European leaders angry with his country's strikes.
Putin was in Paris for talks on Ukraine but faced criticism over Russia's involvement in Syria.
ITV News correspondent Dan Rivers reports:
A surge in military activities has forced the United Nations to halt planned humanitarian operations in Syria agreed under a ceasefire agreement.
Aid activities, including evacuations of wounded, had been planned in Zabadani, a town surrounded by pro-government forces near the Lebanon border, and in rebel-besieged Shi'ite villages in the northwestern province of Idlib (Foua and Kefraya) in the deal agreed with UN help and backed by Iran and Turkey.
"The UN calls on all concerned parties to fulfil their responsibilities in the protection of civilians and reach the necessary understandings in order to implement this agreement as soon as possible," a spokeswoman for UN envoy for Syria Staffan de Mistura said in a statement.
Military air strikes in Syria will not work unless they are coordinated with the government, the country's Foreign Minister has told the United Nations.
In a speech to the General Assembly on Friday, Walid al-Moualem also questioned the value of political negotiations and effectively ruled out any elections "while fighting terrorism".
"Terrorism cannot be fought only from the air, and all of the previous operations to combat it have only served its spread and outbreak," Moualem said.
"Air strikes are useless unless they are conducted in cooperation with the Syrian army, the only force in Syria that is combating terrorism."
The US-led coalition conducted eight air strikes on Islamic State targets in Syria on Thursday.
A statement from the Combined Joint Task Force said that six of the air attacks were in the east of the country near the city of Al Hasakah, hitting tactical units, vehicles and equipment.
The coalition action came as Russian air force jets continued to bomb targets in the country that are not regarded as IS areas but those held by other forces opposed to the regime of Bashar al-Assad.
Islamic State attacked Syrian government-held areas in the eastern city of Deir al-Zor and an air base south of the city on Friday, according to a monitoring group.
Government warplanes bombarded another area of the city and around the air base, the Syrian Observatory for Human Rights said.
The attacks comes a day after Russian jets struck parts of Deir al-Zor province held by Islamic State.