As corporate net-zero pledges multiply, concerns about their credibility and potential for greenwashing are rising. This study is the first to develop a framework specifically tailored to assessing greenwashing in climate and net-zero pledges, combining disclosures, implementation plans, performance data, and lobbying activity, and to apply it at scale to more than 4000 companies. Using data from CDP, InfluenceMap, and the Net Zero Tracker, this analysis offers the largest empirical assessment of its kind. We identify greenwashing risk across seven dimensions, including missing interim targets, Scope 3 exclusion, offset reliance, and misaligned lobbying. We find 96% of pledging companies exhibit at least one risk indicator, with Scope 3 gaps, poor planning, and offsets most common. Greenwashing risk indicators are only weakly correlated, although higher target ambition is modestly associated with fewer red flags on some dimensions, such as Scope 3 coverage and lobbying. Sectoral and regional patterns also emerge, with lobbying-related risks less prevalent among European firms than elsewhere. Our approach advances the evidence base and supports stronger standards and oversight for corporate climate accountability.