Germany could ban fracking until at least 2021 and strictly regulate the use of any such technology in future under policy proposals drawn up by the economy and environment ministers.

Economy Minister Sigmar Gabriel and Environment Minister Barbara Hendricks in a letter laid out government plans to outlaw hydraulic fracturing above a depth of 3,000 metres (9,800 feet) for the next seven years.

Fracking is a technique in which water is injected at very high pressure into a wellbore to fracture deep-rock formations and extract deposits of natural gas and oil.

Germany's reserves of shale oil and gas are shallower than 3,000 metres.

It remains highly controversial in Germany because of concerns it can contaminate water supplies and damage the environment.

In a policy paper sent to lawmakers in their Social Democratic Party, a copy of which was obtained by AFP, Gabriel and Hendricks insisted that they "take people's concerns very seriously".

"What we want is for this debate to be carried out rationally on the basis of scientifically verified information. Protection of health and water has absolute priority," it stated.

The ban would then be reviewed in 2021 to take into account the scientific analysis of fracturing technology by that point, the ministers said.

Conventional or low-volume fracking for gas has been in use in Germany since the 1960s.

In principle it would remain possible in the future but would be subjected to "supplementary regulation", including rules on the substances used, the ministers' policy paper stated.

In effect, however, no permits for conventional fracking have been issued in Germany for a long time because of controversy surrounding the technique.

German industry, notably the chemical sector, is backing the use of fracking in order to cut energy costs.