A plan to make it obligatory to display crosses in Bavaria's government buildings has drawn an angry reaction from opposition politicians and one prominent cleric accused the regional government of 'hypocrisy' ahead of an election.

The conservative Christian Social Union (CSU) party – which is allied with German Chancellor Angela Merkel's conservatives at a national level – faces a stiff challenge from the far-right Alternative for Germany (AfD) party in the October vote.

Premier Markus Soeder's proposal to display the Christian symbol in all regional government buildings is almost certain to be challenged in court for breaching religious neutrality laws, according to Reuters.

But Soeder said the crucifix was being displayed not as a Christian symbol but as a symbol of the identity of Bavaria, Germany's richest and most conservative state.

'We want to give a clear signal that people have a desire to stress their identity,' he said after being photographed affixing an ornate wooden cross, the gift of a former Munich cardinal, to a wall in the premier's office.

The CSU is facing a rising challenge from the far right after governing Bavaria without interruption for more than 50 years and Soeder is under pressure to show he can preserve the dominance that makes his party a powerful lobbyist for its home state in Merkel's Berlin government.

The south-eastern state was on the front line of the migrant crisis of 2015, when over a million people fleeing war and poverty in the Middle East, Africa and Central Asia arrived in Germany, fueling support for the AfD.

The CSU has distanced itself from Merkel's decision to admit the refugees. Former premier Horst Seehofer, now federal interior minister, made waves on assuming his new office by stating that Islam 'does not belong to Germany'.

But the AfD, which campaigns against Muslim immigration, dismissed the cross proposal as 'the usual gesture politics'.

'The Christian cross is being turned into an election accessory, while the conservatives refuse to protect our basic values with real actions,' the AfD's co-leader Alice Weidel said in a statement today.

Even clerics were critical of the plan. 'Many see as a provocation and a hypocrisy the way you speak about Christianity,' wrote Burkhard Hose, a priest who ministers to the students of Wuerzburg University, in an open letter to Soeder.

'Stop this misuse of Christianity and its symbols as a supposed bulwark against Islam,' he added.

Additional reporting by Reuters.