German Chancellor Angela Merkel's conservatives and the centre-left Social Democrats (SPD) were neck-and-neck in the latest INSA poll for Bild newspaper, published six months before a national election.

The conservatives gained one percentage point to 32 per cent while the SPD was unchanged on 32 per cent.

The right-wing Alternative for Germany (AfD) was on 11 per cent while the far-left Linke was on 8.5 per cent and the Greens were on 6.5 percent. The pro-business Free Democrats (FDP) were on 6 percent.

The poll comes a day after Merkel's conservatives won a regional election in the western state of Saarland, a setback for their SPD rivals and boosting her prospects of winning a fourth term in September's national election.

The survey of 2,034 people was carried out from March 24 to March 27.