Stopping Google Leads

Hi All,

This is only a recent problem for me, but I've noticed on a semi-regular basis that when I do a google search and click on a result I get re-directed to another site.

When I click back I am told that it was something called 'google leads' and that i can click to turn it off, which I do. But a few hours later, it is back.

any idea how to swtich this off?

Thanks