The gas-rich state of Qatar has spent as much as $3bn over the past two years supporting the rebellion in Syria, far exceeding any other government, but is now being nudged aside by Saudi Arabia as the prime source of arms to rebels.

The cost of Qatar’s intervention, its latest push to back an Arab revolt, amounts to a fraction of its international investment portfolio. But its financial support for the revolution that has turned into a vicious civil war dramatically overshadows western backing for the opposition.

In dozens of interviews with the Financial Times conducted in recent weeks, rebel leaders both abroad and within Syria as well as regional and western officials detailed Qatar’s role in the Syrian conflict, a source of mounting controversy.

The small state with a gargantuan appetite is the biggest donor to the political opposition, providing generous refugee packages to defectors (one estimate puts it at $50,000 a year for a defector and his family) and has provided vast amounts of humanitarian support.

In September, many rebels in Syria’s Aleppo province received a one-off payment of $150 courtesy of Qatar. Sources close to the Qatari government say total spending has reached as much as $3bn, while rebel and diplomatic sources put the figure at $1bn at most.

For Qatar, owner of the world’s third-largest gas reserves, its intervention in Syria is part of an aggressive quest for global recognition and is merely the latest chapter in its attempt to establish itself as a major player in the region, following its backing of Libya’s rebels who overthrew Muammer Gaddafi in 2011.

According to the Stockholm International Peace Research Institute, which tracks arms transfers, Qatar has sent the most weapons deliveries to Syria, with more than 70 military cargo flights into neighbouring Turkey between April 2012 and March this year.

But though its approach is driven more by pragmatism and opportunism, than ideology, Qatar has become entangled in the polarised politics of the region, setting off scathing criticism. “You can’t buy a revolution,” says an opposition businessman.

Qatar’s support for Islamist groups in the Arab world, which puts it at odds with its peers in the Gulf states, has fuelled rivalry with Saudi Arabia. Hamad bin Khalifa al-Thani, Qatar’s ruling emir, “wants to be the Arab world’s Islamist (Gamal) Abdelnasser”, said an Arab politician, referring to Egypt’s fiery late president and devoted pan-Arab leader.

Qatar’s intervention is coming under mounting scrutiny. Regional rivals contend it is using its financial firepower simply to buy future influence and that it has ended up splintering Syria’s opposition. Against this backdrop Saudi Arabia, which until now has been a more deliberate backer of Syria’s rebels, has stepped up its involvement.

Recent tensions over the opposition’s election of an interim prime minister who won the support of Syria’s Muslim Brotherhood has also driven Saudi Arabia to tighten its relationship to the political opposition, a job it had largely left in the hands of Qatar.

The relegation of Qatar to second place in providing weapons follows concern in the West and among other Arab states that weapons it supplies could fall into the hands of an al-Qaeda-linked group, Jabhat al-Nusrah.

Diplomats also say the Qataris have had trouble securing a steady supply of arms, something the Saudis have been able to do via their more developed networks.

A supply route across Jordan’s border to southern Syria has opened up in recent months. The Jordanian government, which is terrified of jihadis getting the upper hand in its neighbour, has been reluctantly allowing Saudi deliveries.

The west’s reluctance to intervene more forcefully in Syria has all but left Bashar al-Assad’s opponents reliant for support on Qatar, Saudi Arabia and Turkey though since late last year, the United Arab Emirates and Jordan have joined the rebels’ backers as junior partners.

Khalid al-Attiyah, Qatar’s state minister for foreign affairs, who handles its Syrian policy, dismissed talk of rivalry with the Saudis and denied allegations that Qatar’s support for the rebels has splintered Syria’s opposition and weakened nascent institutions.

In an interview with the Financial Times, he said every move Qatar has made has been in conjunction with the Friends of Syria group of Arab and western nations, not alone. “Our problem in Qatar is that we don’t have a hidden agenda so people start fixing you one,” he said

How Qatar seized control of the Syrian revolution - see the May 18, weekend edition