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July 14 (Reuters) - Saba Capital Management has become the largest shareholder in Workspace Group WKP.L, strengthening the activist investor's campaign for strategic reforms at the office-space provider.

A filing on Tuesday showed that Saba has raised its stake in Workspace to 29.1% from 28.2%. It has steadily built its position in the company this year, more than doubling from a 13.5% holding in January.

In June, the firm sought to replace Workspace's non-executive directors, arguing that the company's roughly 50% discount to net asset value reflected years of underperformance and strategic missteps. It also said it had identified a disposal roadmap, covering 56 properties.

Workspace last week urged its shareholders to vote against Saba's proposals at its annual general meeting later this month, adding that the investor's plan was "high-risk, short-sighted and not suitable for the company."

Last month, Workspace unveiled a "transformation to an earnings-focused business" strategy, aiming to reinvest proceeds from asset disposals into property upgrades to boost rental income and drive long-term value creation.

Saba's latest stake increase leaves it just below the 30% threshold that would trigger a mandatory takeover offer for Workspace under UK takeover rules.

Saba Capital declined to comment on any potential offers for Workspace, while Workspace did not immediately respond to a Reuters request for comment.