Arsenal and Chelsea have been warned they must add to their squads if they are to mount a title challenge this season.
Antonio Conte's Blues romped to the championship last season, but the Italian has only recruited Alvaro Morata, in a club record £70million deal, as well as Antonio Rudiger and Tiemoue Bakayako.
However, Premier League legend Shearer believes they don't have enough strength in depth in the squad to compete on all fronts.
"Chelsea have 13 or 14 very good players who will match anyone. But with Champions League football this season, they are going to need more if they want to compete on all fronts" Shearer wrote in his column in The Sun.
"They would need a lot of luck with injuries to get through the campaign and be successful with the squad they have at the moment. I think they still need at least two or three new additions between now and the end of the transfer window."
Furthermore, Shearer has issued a warning to Arsene Wenger and Arsenal if they want to challenge for the title.
The Gunners missed out on a place in the top four last term, and despite bringing in Alexandre Lacazette, the former Blackburn and Newcastle forward insists they don't have enough to challenge at the top.
He added: "Lacazette and yesterday's goalscorer Sead Kolasinac, are their only two signings this summer. That is not enough for The Gunners this season if they want to be challenging for the title, which is ultimately what their supporters want."
With Manchester City and Manchester United splashing the cash and with more signings expected, the London clubs could face a tough season unless they bring in players before the end of the transfer window.