Russian voters' trust in President Vladimir Putin has plunged 20 per cent in a year amid popular discontent over a rise in the retirement age, a poll revealed today.

It is the lowest rating for Putin since 2014, before he enjoyed a surge in popularity over the annexation of Crimea from Ukraine.

The survey by the independent Levada Centre found that trust in Putin has fallen to 39 per cent - a drop of nine percentage points since June and 20 percentage points since November 2017.

Russian President Vladimir Putin addresses the India-Russia Business Summit in New Delhi, India, on Friday

Still, only 13 per cent of Russians said they definitely did not trust Putin, according to the poll carried out between September 20 and 26.

Analysts did not speculate on whether the Novichok scandal in which two Kremlin hitmen poisoned a double agent in Salisbury contributed to the decline in trust.

Hours after the poll result was announced, the Levada Centre's website was down, with a message reading: 'Error establishing a database connection'.

Moscow Times journalist Pjotr Sauer speculated the Kremlin hacked it due to 'Putin's obsession with ratings.'

The veteran Russian leader last week signed into law a bill that will gradually increase the state retirement age to 60 for women and 65 for men, the first such increase since the 1930s.

Most Russians are deeply opposed to the reforms, which sparked rare street protests.

'People think the government is trying to solve its problems at the public's expense. It has made an attempt to take something people consider to be theirs: pension savings,' Levada Centre director Lev Gudkov told the Vedomosti business daily.

He said social tensions have been building since the end of last year because of a variety of factors including a fall in real earnings and rising prices.

While Putin easily won the March presidential election with more than 76 percent of the vote, public discontent about the pension reforms meant 'all elements of concern (about him) were lumped together', Gudkov said.

Putin shakes hands with the Indian Prime Minister Narendra Modi, during the India-Russia Business Summit in New Delhi

This led to a fall in trust not only in Putin but also in his allies: Defence Minister Sergei Shoigu and Foreign Minister Sergei Lavrov, he added.

Putin's personal style of rule means he 'cannot hand over responsibility to someone else' for unpopular decisions, political analyst Dmitry Orlov told Vedomosti.

Putin's lowest ever rating in such a Levada poll was in August 2013, when just 30 percent named him as a trusted politician.

He had suffered a long period of decline in support after the 2008 economic crisis and a wave of protests in 2011-12.

Putin's spokesman Dmitry Peskov declined to comment to Vedomosti on the latest poll.