Twitter stock was 'overrated' but will now see some upside, major shareholder Steve Ballmer says

Twitter is fixable with the stock likely to see an upside, major shareholder Steve Ballmer told CNBC on Tuesday, adding that he is also open to the social media company being acquired.

The ex-Microsoft chief executive said that Twitter's stock was "overrated" at one point and that he bought shares in the company at a higher price than the current $14.40 value. But shares are likely to rise from here if CEO Jack Dorsey innovates with the product.

"The first thing I'd tell him (Dorsey) to do is probably ignore his short-term stock price because at the end of the day what they have to do is worry about the product innovation and they have to worry about the ease of use and marketing, those are two things I've been consistent about," Ballmer said in a TV interview.

"As those things get better I think people will recognize it and the stock will show upside."

Twitter's share price is down more than 18 percent in the last 12 months as it has struggled to grow its user base and make money. Dorsey has faced questions over his leadership of the embattled firm but told CNBC in a recent interview that he would do "whatever it takes" to make sure Twitter succeeded.

In a separate recent interview with CNBC, Ballmer said he thinks Dorsey should focus solely on Twitter, rather than on his other company Square as well.

"Running two companies is not the best idea," Ballmer said. "And I'll stand by the notion that Jack's a very creative, innovative guy, as well evidenced by the fact that he started two amazing companies. ... I give him credit for that, and I think now's the time to focus down, at least from my perspective, on the stock I own."

Last year, Twitter was also reportedly approached by a number of companies interested in acquiring the company including Salesforce and Google.

Ballmer said that he "would remain open to offers if they come in".