The 84-year-old entrepreneur, who started his Tindle Newspapers group with £300 of demob money, now owns 6.36pc of the Edinburgh-based regional publishing giant.
Last month Sir Ray seized on JP’s low share price to increase his stake in the company to 4.36pc.
Now with JP shares still valued at 5p he has upped his shareholding by a further 2pc.
Only two individual shareholders now own more of JP than Sir Ray – Malaysian billionaire Ananda Krishnan’s PanOcean Management with 20pc, and Orbis Holdings with 10.7pc.
In an interview with The Times, Sir Ray denied he was planning a takeover bid for JP, but confirmed that he would be interested in increasing his stake again if the opportunity arose.
“My opinion is that newspapers are undervalued at the moment. I know that people out in the sticks still stand by their local papers,” he said.
He said shares in Johnston Press had endured “one hell of a drop” in recent years, which he did not believe was justified.
“They have a lot of papers, good papers. They are all good friends and they are coping well with the problem,” he added.
“A small upturn in the economy would put the business ‘back on the straight and narrow’. They are undervalued, so I decided to buy.”
No-one at Johnston Press has so far been available for comment.