Waveney District Council rejected the application for the 24MW project on grounds of harm to the landscape in February, after developer Lark Energy refused to reduce its size. The developer's appeal was then recovered by Eric Pickles for his own determination.
Inspector Neil Pope recommended that the appeal be allowed, contending that the harm to the character and appearance of the landscape was "limited".
But Pickles' decision letter stated: "The secretary of state agrees with the inspector that the harm to the character and appearance of the area would not amount to significant adverse effects but, nevertheless, considers the effect on the character of the site, although limited, would be adverse."
Leonie Greene, head of external affairs at the Solar Trade Association, said: "Given the mood music and politics in parts of the government, we're concerned that there's a political agenda."
David Cox, partner at law firm Dentons, said that it was unusual for a secretary of state to overrule an inspector's recommendation on landscape grounds. "That isn't what normally happens and it shouldn't happen," he said.
Pickles' need to give teeth to his recently issued guidance on renewable energy - which said that the need for renewable energy would not override views of local people and concerns over landscape and heritage - was behind the decision, Cox suggested.
The communities secretary's decision on the solar farm was based on the impact on the site itself rather than the wider landscape, said Paul Maile, partner at law firm Eversheds.
"This is a grave concern to developers of all renewables' projects if that's where the secretary of state is setting the bar in terms of acceptability. Undoubtedly that is a very low level of impact. You'd expect a raft of refusals," said Maile.
Earlier this month, Pickles pledged to recover more renewable energy appeal cases for his own determination. He then recovered 17 wind energy applications, including several for single turbines