All new apps will be scanned by malware-spotting tools from three cyber-security companies as well as Google's own in-house system.

Google said it needed help because the number of apps being uploaded was too large for it to handle alone.

Nasty Play apps can hit lots of people. Malicious code found in June was in apps downloaded 400 million times.

Security companies Zimperium, Eset and Lookout will work together on what Google has called the App Defense Alliance.

The four partners will set up a combined scanning system that will scrutinise apps as they pass through Google's pipeline on the way to being offered to Android users via the Play store.

Working from massive databases of known malware, behavioural clues and machine-learning models of novel threats the scanners will look for trojans, adware, ransomware, banking malware and phishing attacks.

"On the malware side, we haven't really had a way to scale as much as we've wanted to scale," Dave Kleidermacher, Google's vice-president of Android security, told Wired magazine.

Mr Kleidermacher added there were so many apps being developed, even making a "1% incremental improvement" could make a difference.

The scanning system is the latest in a series of steps Google has taken in its bid to do a better job of policing the Play store.

In April, it announced more rigorous checks for developers to root out "bad faith" coders who produced and uploaded malicious or fraudulent apps.